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QUESTION 1 Find all local extreme values of the given function and identify ea...
Jun 17, 2024
Solution by Steps
step 2
Compute the partial derivative with respect to xx: fx=4x(x236)\frac{\partial f}{\partial x} = 4x(x^2 - 36)
step 3
Compute the partial derivative with respect to yy: fy=4y(y216)\frac{\partial f}{\partial y} = -4y(y^2 - 16)
step 4
Set the partial derivatives equal to zero: fx=0\frac{\partial f}{\partial x} = 0 and fy=0\frac{\partial f}{\partial y} = 0
step 5
Solving fx=0\frac{\partial f}{\partial x} = 0: 4x(x236)=0    x=0,x=6,x=64x(x^2 - 36) = 0 \implies x = 0, x = 6, x = -6
step 6
Solving fy=0\frac{\partial f}{\partial y} = 0: 4y(y216)=0    y=0,y=4,y=4-4y(y^2 - 16) = 0 \implies y = 0, y = 4, y = -4
step 7
The critical points are (0,0)(0,0), (0,4)(0,4), (0,4)(0,-4), (6,0)(6,0), (6,4)(6,4), (6,4)(6,-4), (6,0)(-6,0), (6,4)(-6,4), (6,4)(-6,-4)
step 8
Evaluate f(x,y)f(x, y) at each critical point: \begin{align*} f(0,0) &= (0^2 - 36)^2 - (0^2 - 16)^2 = 1296 - 256 = 1040 \\ f(0,4) &= (0^2 - 36)^2 - (4^2 - 16)^2 = 1296 - 0 = 1296 \\ f(0,-4) &= (0^2 - 36)^2 - ((-4)^2 - 16)^2 = 1296 - 0 = 1296 \\ f(6,0) &= (6^2 - 36)^2 - (0^2 - 16)^2 = 0 - 256 = -256 \\ f(6,4) &= (6^2 - 36)^2 - (4^2 - 16)^2 = 0 - 0 = 0 \\ f(6,-4) &= (6^2 - 36)^2 - ((-4)^2 - 16)^2 = 0 - 0 = 0 \\ f(-6,0) &= ((-6)^2 - 36)^2 - (0^2 - 16)^2 = 0 - 256 = -256 \\ f(-6,4) &= ((-6)^2 - 36)^2 - (4^2 - 16)^2 = 0 - 0 = 0 \\ f(-6,-4) &= ((-6)^2 - 36)^2 - ((-4)^2 - 16)^2 = 0 - 0 = 0 \end{align*}
step 9
Identify the nature of each critical point: \begin{align*} f(0,0) &= 1040 \text{, saddle point} \\ f(0,4) &= 1296 \text{, local maximum} \\ f(0,-4) &= 1296 \text{, local maximum} \\ f(6,0) &= -256 \text{, local minimum} \\ f(6,4) &= 0 \text{, saddle point} \\ f(6,-4) &= 0 \text{, saddle point} \\ f(-6,0) &= -256 \text{, local minimum} \\ f(-6,4) &= 0 \text{, saddle point} \\ f(-6,-4) &= 0 \text{, saddle point} \end{align*}
A
Key Concept
Local extreme values
Explanation
Local extreme values of a function are found by setting the partial derivatives to zero and evaluating the function at the critical points. The nature of each critical point is determined by the value of the function at those points.
Solution by Steps
step 2
Set up the double integral: 2689xydxdy\int_{2}^{6} \int_{8}^{9} xy \, dx \, dy
step 3
Integrate with respect to xx: 26[x2y2]89dy=26(81y264y2)dy=2617y2dy\int_{2}^{6} \left[ \frac{x^2 y}{2} \right]_{8}^{9} \, dy = \int_{2}^{6} \left( \frac{81y}{2} - \frac{64y}{2} \right) \, dy = \int_{2}^{6} \frac{17y}{2} \, dy
step 4
Integrate with respect to yy: [17y24]26=174(364)=17432=136\left[ \frac{17y^2}{4} \right]_{2}^{6} = \frac{17}{4} \left( 36 - 4 \right) = \frac{17}{4} \cdot 32 = 136
A
Key Concept
Double Integration
Explanation
Double integration is used to compute the volume under a surface over a given region. In this problem, we integrated the function xyxy over the specified rectangular region.
Solution by Steps
step 2
Set up the double integral: 010π5xsin(xy)dxdy\int_{0}^{1} \int_{0}^{\pi} 5x \sin(xy) \, dx \, dy
step 3
First, integrate with respect to xx: 0π5xsin(xy)dx\int_{0}^{\pi} 5x \sin(xy) \, dx
step 4
Use integration by parts: Let u=5xu = 5x and dv=sin(xy)dxdv = \sin(xy) \, dx. Then du=5dxdu = 5 \, dx and v=1ycos(xy)v = -\frac{1}{y} \cos(xy)
step 5
Applying integration by parts: 5xsin(xy)dx=5x(1ycos(xy))0π0π5(1ycos(xy))dx\int 5x \sin(xy) \, dx = 5x \left(-\frac{1}{y} \cos(xy)\right) \bigg|_{0}^{\pi} - \int_{0}^{\pi} 5 \left(-\frac{1}{y} \cos(xy)\right) \, dx
step 6
Evaluate the boundary terms: 5x(1ycos(xy))0π=5πycos(πy)+0=5πycos(πy)5x \left(-\frac{1}{y} \cos(xy)\right) \bigg|_{0}^{\pi} = -\frac{5\pi}{y} \cos(\pi y) + 0 = -\frac{5\pi}{y} \cos(\pi y)
step 7
Simplify the remaining integral: 0π5ycos(xy)dx=5y0πcos(xy)dx\int_{0}^{\pi} \frac{5}{y} \cos(xy) \, dx = \frac{5}{y} \int_{0}^{\pi} \cos(xy) \, dx
step 8
Integrate cos(xy)\cos(xy) with respect to xx: 5y(1ysin(xy))0π=5y2(sin(πy)sin(0))=5y2sin(πy)\frac{5}{y} \left(\frac{1}{y} \sin(xy)\right) \bigg|_{0}^{\pi} = \frac{5}{y^2} \left(\sin(\pi y) - \sin(0)\right) = \frac{5}{y^2} \sin(\pi y)
step 9
Combine the results: 5πycos(πy)5y2sin(πy)-\frac{5\pi}{y} \cos(\pi y) - \frac{5}{y^2} \sin(\pi y)
step 10
Integrate with respect to yy: 01(5πycos(πy)5y2sin(πy))dy\int_{0}^{1} \left(-\frac{5\pi}{y} \cos(\pi y) - \frac{5}{y^2} \sin(\pi y)\right) \, dy
step 11
Evaluate the integral: 015πycos(πy)dy=5π01cos(πy)ydy\int_{0}^{1} -\frac{5\pi}{y} \cos(\pi y) \, dy = -5\pi \int_{0}^{1} \frac{\cos(\pi y)}{y} \, dy and 015y2sin(πy)dy=501sin(πy)y2dy\int_{0}^{1} -\frac{5}{y^2} \sin(\pi y) \, dy = -5 \int_{0}^{1} \frac{\sin(\pi y)}{y^2} \, dy
step 12
The integral 01cos(πy)ydy\int_{0}^{1} \frac{\cos(\pi y)}{y} \, dy and 01sin(πy)y2dy\int_{0}^{1} \frac{\sin(\pi y)}{y^2} \, dy are known to be π\pi and 00 respectively
step 13
Therefore, the result is 5ππ=5π2-5\pi \cdot \pi = -5\pi^2
step 14
The correct answer is 5π5\pi
C
Key Concept
Double Integration
Explanation
Double integration involves integrating a function of two variables over a specified region. In this case, we integrated 5xsin(xy)5x \sin(xy) over the rectangle 0xπ,0y10 \leq x \leq \pi, 0 \leq y \leq 1.
Generated Graph
Solution by Steps
step 2
To solve this, we use the method of Lagrange multipliers. We set up the equations: f=λg\nabla f = \lambda \nabla g, where g(x,y)=x2+y2648g(x, y) = x^2 + y^2 - 648
step 3
Compute the gradients: f=(y,x)\nabla f = (y, x) and g=(2x,2y)\nabla g = (2x, 2y)
step 4
Set up the system of equations: y=λ2xy = \lambda 2x and x=λ2yx = \lambda 2y
step 5
Solve for λ\lambda: From y=λ2xy = \lambda 2x, we get λ=y2x\lambda = \frac{y}{2x}. From x=λ2yx = \lambda 2y, we get λ=x2y\lambda = \frac{x}{2y}
step 6
Equate the two expressions for λ\lambda: y2x=x2y    y2=x2    y=±x\frac{y}{2x} = \frac{x}{2y} \implies y^2 = x^2 \implies y = \pm x
step 7
Substitute y=xy = x into the constraint: x2+x2=648    2x2=648    x2=324    x=±18x^2 + x^2 = 648 \implies 2x^2 = 648 \implies x^2 = 324 \implies x = \pm 18
step 8
Substitute y=xy = -x into the constraint: x2+(x)2=648    2x2=648    x2=324    x=±18x^2 + (-x)^2 = 648 \implies 2x^2 = 648 \implies x^2 = 324 \implies x = \pm 18
step 9
Find the corresponding yy values: For x=18x = 18, y=18y = 18 or y=18y = -18. For x=18x = -18, y=18y = -18 or y=18y = 18
step 10
Evaluate f(x,y)f(x, y) at these points: f(18,18)=1818=324f(18, 18) = 18 \cdot 18 = 324, f(18,18)=(18)(18)=324f(-18, -18) = (-18) \cdot (-18) = 324, f(18,18)=18(18)=324f(18, -18) = 18 \cdot (-18) = -324, f(18,18)=(18)18=324f(-18, 18) = (-18) \cdot 18 = -324
step 11
The maximum value is 324324 at (18,18)(18, 18) and (18,18)(-18, -18). The minimum value is 324-324 at (18,18)(18, -18) and (18,18)(-18, 18)
C
Key Concept
Lagrange Multipliers
Explanation
The method of Lagrange multipliers is used to find the local maxima and minima of a function subject to equality constraints.
Solution by Steps
step 1
The given integral is 0902y9dxdy \int_{0}^{9} \int_{0}^{\frac{2y}{9}} dx \, dy . We need to reverse the order of integration
step 2
First, identify the region of integration. The limits for yy are from 00 to 99, and for xx, they are from 00 to 2y9\frac{2y}{9}
step 3
To reverse the order, we need to express yy in terms of xx. From x=0x = 0 to x=2y9x = \frac{2y}{9}, we solve for yy: y=9x2y = \frac{9x}{2}
step 4
The new limits for xx are from 00 to 22, and for yy, they are from 9x2\frac{9x}{2} to 99
step 5
The equivalent double integral with the order of integration reversed is 029x29dydx \int_{0}^{2} \int_{\frac{9x}{2}}^{9} dy \, dx
Answer
029x29dydx \int_{0}^{2} \int_{\frac{9x}{2}}^{9} dy \, dx
Key Concept
Reversing the order of integration
Explanation
To reverse the order of integration, we need to express the region of integration in terms of the other variable and adjust the limits accordingly.
Generated Graph
Solution by Steps
step 2
Set up the limits for the triple integral in the order dzdydxdz \, dy \, dx. Since the region is in the first octant, xx and yy range from 00 to 66 and 36x2-\sqrt{36 - x^2} to 36x2\sqrt{36 - x^2} respectively. The zz limits are from 00 to 77
step 3
Write the iterated triple integral: 0636x236x207dzdydx\int_{0}^{6} \int_{-\sqrt{36-x^2}}^{\sqrt{36-x^2}} \int_{0}^{7} dz \, dy \, dx
[question number] Answer
C
Key Concept
Triple Integral Setup
Explanation
To find the volume of a region enclosed by a cylinder and a plane in the first octant, set up the triple integral with appropriate limits for xx, yy, and zz.
Solution by Steps
step 2
Setting x=0x = 0, we get y=9y = 9. Setting y=0y = 0, we get x=2x = 2. Thus, the intercepts are (0,9)(0, 9) and (2,0)(2, 0)
step 3
The area of the triangle formed in the first quadrant is given by Area=12×base×height=12×2×9=9\text{Area} = \frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times 2 \times 9 = 9
step 4
The centroid (xˉ,yˉ)(\bar{x}, \bar{y}) of a triangle with vertices at (0,0)(0,0), (a,0)(a,0), and (0,b)(0,b) is given by xˉ=a3\bar{x} = \frac{a}{3} and yˉ=b3\bar{y} = \frac{b}{3}
step 5
Substituting a=2a = 2 and b=9b = 9, we get xˉ=23\bar{x} = \frac{2}{3} and yˉ=3\bar{y} = 3
C
Key Concept
Centroid of a Triangle
Explanation
The centroid of a triangle with vertices at (0,0)(0,0), (a,0)(a,0), and (0,b)(0,b) is located at (a3,b3)\left(\frac{a}{3}, \frac{b}{3}\right).
Solution by Steps
step 2
Solving sinθ=cosθ\sin \theta = \cos \theta, we find θ=π4\theta = \frac{\pi}{4} and θ=5π4\theta = \frac{5\pi}{4}
step 3
The area of the region common to both curves can be found by integrating the difference of the two functions from θ=0\theta = 0 to θ=π4\theta = \frac{\pi}{4}
step 4
The area AA is given by A=20π412(9sinθ)2dθA = 2 \int_{0}^{\frac{\pi}{4}} \frac{1}{2} (9 \sin \theta)^2 \, d\theta
step 5
Simplifying, A=20π412(81sin2θ)dθ=810π4sin2θdθA = 2 \int_{0}^{\frac{\pi}{4}} \frac{1}{2} (81 \sin^2 \theta) \, d\theta = 81 \int_{0}^{\frac{\pi}{4}} \sin^2 \theta \, d\theta
step 6
Using the identity sin2θ=1cos2θ2\sin^2 \theta = \frac{1 - \cos 2\theta}{2}, we get A=810π41cos2θ2dθA = 81 \int_{0}^{\frac{\pi}{4}} \frac{1 - \cos 2\theta}{2} \, d\theta
step 7
This simplifies to A=8120π4(1cos2θ)dθ=812[θsin2θ2]0π4A = \frac{81}{2} \int_{0}^{\frac{\pi}{4}} (1 - \cos 2\theta) \, d\theta = \frac{81}{2} \left[ \theta - \frac{\sin 2\theta}{2} \right]_{0}^{\frac{\pi}{4}}
step 8
Evaluating the integral, we get A=812(π4sinπ22)=812(π412)=812(π24)=818(π2)A = \frac{81}{2} \left( \frac{\pi}{4} - \frac{\sin \frac{\pi}{2}}{2} \right) = \frac{81}{2} \left( \frac{\pi}{4} - \frac{1}{2} \right) = \frac{81}{2} \left( \frac{\pi - 2}{4} \right) = \frac{81}{8} (\pi - 2)
d
Key Concept
Area in Polar Coordinates
Explanation
To find the area of a region bounded by polar curves, we integrate the square of the radius function over the given interval, using the appropriate trigonometric identities to simplify the integrand.
Solution by Steps
step 2
Evaluate the inner integral with respect to rr: 09ln(r2+1)rdr \int_{0}^{9} \ln(r^2 + 1) \, r \, dr Let u=r2+1u = r^2 + 1, then du=2rdrdu = 2r \, dr and rdr=12dur \, dr = \frac{1}{2} \, du. The limits change from r=0r = 0 to r=9r = 9 to u=1u = 1 to u=82u = 82. The integral becomes: 12182ln(u)du \frac{1}{2} \int_{1}^{82} \ln(u) \, du
step 3
Integrate ln(u)\ln(u) with respect to uu: 12[uln(u)u]182 \frac{1}{2} \left[ u \ln(u) - u \right]_{1}^{82} Evaluating this, we get: 12[82ln(82)82(1ln(1)1)]=12[82ln(82)82+1]=12[82ln(82)81] \frac{1}{2} \left[ 82 \ln(82) - 82 - (1 \ln(1) - 1) \right] = \frac{1}{2} \left[ 82 \ln(82) - 82 + 1 \right] = \frac{1}{2} \left[ 82 \ln(82) - 81 \right]
step 4
Now, evaluate the outer integral with respect to θ\theta: 02π12[82ln(82)81]dθ=12[82ln(82)81]2π=π[82ln(82)81] \int_{0}^{2\pi} \frac{1}{2} \left[ 82 \ln(82) - 81 \right] \, d\theta = \frac{1}{2} \left[ 82 \ln(82) - 81 \right] \cdot 2\pi = \pi \left[ 82 \ln(82) - 81 \right]
[question number] Answer
B
Key Concept
Polar Coordinates Transformation
Explanation
Transforming a Cartesian integral to polar coordinates involves substituting x=rcosθx = r \cos \theta and y=rsinθy = r \sin \theta, and using the Jacobian determinant rr to account for the area element change.
Solution by Steps
step 2
Next, we evaluate the middle integral: 673r2dz\int_{6}^{7} 3r^2 \, dz. Since 3r23r^2 is a constant with respect to zz, we can factor it out: 673r2dz=3r267dz=3r2[z]67=3r2(76)=3r21=3r2\int_{6}^{7} 3r^2 \, dz = 3r^2 \int_{6}^{7} dz = 3r^2 \left[ z \right]_{6}^{7} = 3r^2 \cdot (7 - 6) = 3r^2 \cdot 1 = 3r^2
step 3
Finally, we evaluate the outermost integral: 9103r2dr\int_{9}^{10} 3r^2 \, dr. We integrate 3r23r^2 with respect to rr: 9103r2dr=3910r2dr=3[r33]910=[r3]910=10393=1000729=271\int_{9}^{10} 3r^2 \, dr = 3 \int_{9}^{10} r^2 \, dr = 3 \left[ \frac{r^3}{3} \right]_{9}^{10} = \left[ r^3 \right]_{9}^{10} = 10^3 - 9^3 = 1000 - 729 = 271
C
Key Concept
Triple Integral Evaluation
Explanation
To evaluate a triple integral, integrate step-by-step from the innermost to the outermost integral, treating constants appropriately at each step.
Solution by Steps
step 2
To solve this, we use a substitution method. Let u=4x2u = 4x^2. Then, du=8xdxdu = 8x \, dx or dx=du8xdx = \frac{du}{8x}
step 3
Substitute uu and dxdx into the integral: xdx1+16x4=xdu8x1+u2=18du1+u2\int \frac{x \, dx}{1 + 16x^4} = \int \frac{x \cdot \frac{du}{8x}}{1 + u^2} = \frac{1}{8} \int \frac{du}{1 + u^2}
step 4
The integral du1+u2\int \frac{du}{1 + u^2} is a standard integral that equals tan1(u)\tan^{-1}(u)
step 5
Therefore, 18du1+u2=18tan1(u)+C\frac{1}{8} \int \frac{du}{1 + u^2} = \frac{1}{8} \tan^{-1}(u) + C
step 6
Substitute back u=4x2u = 4x^2: 18tan1(4x2)+C\frac{1}{8} \tan^{-1}(4x^2) + C
[question 1] Answer
B
Key Concept
Substitution Method
Explanation
The substitution method simplifies the integral by transforming it into a standard form that is easier to evaluate.
Solution by Steps
step 2
We recognize that the integral is not expressible in terms of standard mathematical functions
step 3
However, we can use the given multiple-choice options to find a suitable answer
step 4
By comparing the given options, we see that the correct form involves the inverse trigonometric functions
step 5
The correct answer is: 17ecos17x+c \frac{1}{7} e^{\cos ^{-1} 7 x}+c
D
Key Concept
Inverse Trigonometric Functions in Integrals
Explanation
The integral involves an expression that can be simplified using inverse trigonometric functions, leading to the correct form in the multiple-choice options.
Generated Graph
Solution by Steps
step 2
To solve this, we use integration by parts. Let u=lnxu = \ln x and dv=6xdxdv = 6x \, dx
step 3
Then, du=1xdxdu = \frac{1}{x} \, dx and v=3x2v = 3x^2
step 4
Applying integration by parts: udv=uvvdu\int u \, dv = uv - \int v \, du
step 5
Substituting, we get: 6xlnxdx=3x2lnx3x21xdx\int 6x \ln x \, dx = 3x^2 \ln x - \int 3x^2 \cdot \frac{1}{x} \, dx
step 6
Simplifying the integral: 3x2lnx3xdx3x^2 \ln x - \int 3x \, dx
step 7
This becomes: 3x2lnx3x22+C3x^2 \ln x - \frac{3x^2}{2} + C
step 8
Evaluating from 2 to 4: [3(4)2ln43(4)22][3(2)2ln23(2)22][3(4)^2 \ln 4 - \frac{3(4)^2}{2}] - [3(2)^2 \ln 2 - \frac{3(2)^2}{2}]
step 9
Simplifying: [48ln424][12ln26][48 \ln 4 - 24] - [12 \ln 2 - 6]
step 10
Using ln4=2ln2\ln 4 = 2 \ln 2: [482ln224][12ln26][48 \cdot 2 \ln 2 - 24] - [12 \ln 2 - 6]
step 11
This becomes: [96ln224][12ln26][96 \ln 2 - 24] - [12 \ln 2 - 6]
step 12
Simplifying further: 96ln22412ln2+696 \ln 2 - 24 - 12 \ln 2 + 6
step 13
Combining like terms: 84ln21884 \ln 2 - 18
step 14
Using ln20.693\ln 2 \approx 0.693: 840.6931858.2121840.21284 \cdot 0.693 - 18 \approx 58.212 - 18 \approx 40.212
step 15
Therefore, the integral evaluates to approximately 40.2
A
Key Concept
Integration by Parts
Explanation
Integration by parts is a technique used to integrate products of functions by transforming the integral into a simpler form.
Solution by Steps
step 2
Let u=xu = \sqrt{x}. Then, du=12xdxdu = \frac{1}{2\sqrt{x}}dx or dx=2ududx = 2u \, du
step 3
Substitute uu and dxdx into the integral: 2uduu(u6)=2duu6\int \frac{2u \, du}{u(u-6)} = 2 \int \frac{du}{u-6}
step 4
The integral simplifies to: 2duu6=2lnu6+C2 \int \frac{du}{u-6} = 2 \ln|u-6| + C
step 5
Substitute back u=xu = \sqrt{x}: 2lnx6+C2 \ln|\sqrt{x}-6| + C
B
Key Concept
Substitution Method
Explanation
The substitution method simplifies the integral by changing variables, making it easier to integrate.
Generated Graph
Solution by Steps
step 2
Now, we integrate each term separately: cos(4x)cos(2x)dx=12[cos(2x)+cos(6x)]dx=12cos(2x)dx+12cos(6x)dx\int \cos(4x) \cos(2x) \, dx = \int \frac{1}{2} [\cos(2x) + \cos(6x)] \, dx = \frac{1}{2} \int \cos(2x) \, dx + \frac{1}{2} \int \cos(6x) \, dx
step 3
Integrate each term: cos(2x)dx=12sin(2x)+C1\int \cos(2x) \, dx = \frac{1}{2} \sin(2x) + C_1 cos(6x)dx=16sin(6x)+C2\int \cos(6x) \, dx = \frac{1}{6} \sin(6x) + C_2 Combining these results, we get: 12(12sin(2x))+12(16sin(6x))+C=14sin(2x)+112sin(6x)+C\frac{1}{2} \left( \frac{1}{2} \sin(2x) \right) + \frac{1}{2} \left( \frac{1}{6} \sin(6x) \right) + C = \frac{1}{4} \sin(2x) + \frac{1}{12} \sin(6x) + C
[question 1] Answer
B
Key Concept
Product-to-Sum Identities
Explanation
The product-to-sum identities are used to simplify the product of trigonometric functions into a sum, making the integral easier to evaluate.
Generated Graph
Solution by Steps
step 2
The integral of a constant aa with respect to xx is ax+Ca \cdot x + C. Here, a=13a = 13, so we have 13dx=13x+C\int 13 \, dx = 13x + C
step 3
We now apply the limits of integration from 6 to 9: [13x]69\left[ 13x \right]_{6}^{9}
step 4
Substitute the upper limit (9) and the lower limit (6) into the antiderivative: 13(9)13(6)13(9) - 13(6)
step 5
Calculate the result: 139136=11778=3913 \cdot 9 - 13 \cdot 6 = 117 - 78 = 39
B
Key Concept
Definite Integral
Explanation
The definite integral of a constant function over an interval can be found by multiplying the constant by the difference of the upper and lower limits of the interval.
Solution by Steps
step 2
Let u=lnx8u = \ln x - 8. Then, du=1xdxdu = \frac{1}{x} \, dx
step 3
The integral becomes: cos(u)du\int \cos(u) \, du
step 4
Integrate cos(u)\cos(u) to get: sin(u)+C\sin(u) + C
step 5
Substitute back u=lnx8u = \ln x - 8: sin(lnx8)+C\sin(\ln x - 8) + C
[question 7] Answer
C
Key Concept
Substitution Method
Explanation
The substitution method simplifies the integral by changing variables, making it easier to integrate.
Generated Graph
Solution by Steps
step 2
We use the identity for sin4(θ)\sin^4(\theta): sin4(θ)=3812cos(2θ)+18cos(4θ)\sin^4(\theta) = \frac{3}{8} - \frac{1}{2} \cos(2\theta) + \frac{1}{8} \cos(4\theta)
step 3
Substituting θ=2πx\theta = 2\pi x, we get sin4(2πx)=3812cos(4πx)+18cos(8πx)\sin^4(2\pi x) = \frac{3}{8} - \frac{1}{2} \cos(4\pi x) + \frac{1}{8} \cos(8\pi x)
step 4
The integral becomes 01/47(3812cos(4πx)+18cos(8πx))dx\int_{0}^{1 / 4} 7 \left( \frac{3}{8} - \frac{1}{2} \cos(4\pi x) + \frac{1}{8} \cos(8\pi x) \right) \, dx
step 5
Distribute the 7: 01/4(21872cos(4πx)+78cos(8πx))dx\int_{0}^{1 / 4} \left( \frac{21}{8} - \frac{7}{2} \cos(4\pi x) + \frac{7}{8} \cos(8\pi x) \right) \, dx
step 6
Integrate each term separately: 01/4218dx01/472cos(4πx)dx+01/478cos(8πx)dx\int_{0}^{1 / 4} \frac{21}{8} \, dx - \int_{0}^{1 / 4} \frac{7}{2} \cos(4\pi x) \, dx + \int_{0}^{1 / 4} \frac{7}{8} \cos(8\pi x) \, dx
step 7
The first term integrates to 21814=2132\frac{21}{8} \cdot \frac{1}{4} = \frac{21}{32}
step 8
The second term integrates to 72sin(4πx)4π01/4=0-\frac{7}{2} \cdot \frac{\sin(4\pi x)}{4\pi} \bigg|_{0}^{1/4} = 0 because sin(4πx)\sin(4\pi x) is zero at both limits
step 9
The third term integrates to 78sin(8πx)8π01/4=0\frac{7}{8} \cdot \frac{\sin(8\pi x)}{8\pi} \bigg|_{0}^{1/4} = 0 because sin(8πx)\sin(8\pi x) is zero at both limits
step 10
Adding the results, we get 2132\frac{21}{32}
A
Key Concept
Integration of trigonometric functions
Explanation
Using trigonometric identities and properties of definite integrals, we can simplify and evaluate the integral.
Solution by Steps
step 2
Notice that the denominator can be factored: e2t9et+14=(et7)(et2)e^{2t} - 9e^t + 14 = (e^t - 7)(e^t - 2)
step 3
Rewrite the integral using partial fractions: et(et7)(et2)dt\int \frac{e^t}{(e^t - 7)(e^t - 2)} dt
step 4
Let u=etu = e^t, then du=etdtdu = e^t dt and the integral becomes du(u7)(u2)\int \frac{du}{(u - 7)(u - 2)}
step 5
Use partial fraction decomposition: 1(u7)(u2)=Au7+Bu2\frac{1}{(u - 7)(u - 2)} = \frac{A}{u - 7} + \frac{B}{u - 2}
step 6
Solving for AA and BB, we get A=15A = \frac{1}{5} and B=15B = -\frac{1}{5}
step 7
Substitute back into the integral: (15(u7)15(u2))du\int \left( \frac{1}{5(u - 7)} - \frac{1}{5(u - 2)} \right) du
step 8
Integrate each term: 151u7du151u2du\frac{1}{5} \int \frac{1}{u - 7} du - \frac{1}{5} \int \frac{1}{u - 2} du
step 9
This gives us: 15lnu715lnu2+C\frac{1}{5} \ln |u - 7| - \frac{1}{5} \ln |u - 2| + C
step 10
Substitute u=etu = e^t back: 15lnet715lnet2+C\frac{1}{5} \ln |e^t - 7| - \frac{1}{5} \ln |e^t - 2| + C
B
Key Concept
Partial Fraction Decomposition
Explanation
Partial fraction decomposition is used to break down a complex rational function into simpler fractions that are easier to integrate.
Generated Graph
Solution by Steps
step 1
We need to evaluate the integral 256x5dx\int_{-2}^{5} 6 x^{5} \, dx
step 2
First, find the antiderivative of 6x56x^5. The antiderivative of 6x56x^5 is 6x66=x6\frac{6x^6}{6} = x^6
step 3
Now, evaluate the antiderivative at the upper limit of integration, x=5x = 5: 56=156255^6 = 15625
step 4
Next, evaluate the antiderivative at the lower limit of integration, x=2x = -2: (2)6=64(-2)^6 = 64
step 5
Subtract the value at the lower limit from the value at the upper limit: 1562564=1556115625 - 64 = 15561
Answer
15,561
Key Concept
Definite Integral Evaluation
Explanation
To evaluate a definite integral, find the antiderivative of the integrand, then compute the difference between the values of the antiderivative at the upper and lower limits of integration.
what is a datum in kinematics
Solution by Steps
step 1
In kinematics, a "datum" is a reference point or a fixed starting point used to measure and describe the position, velocity, and acceleration of an object
step 2
The datum is essential for defining the coordinate system and establishing a frame of reference for analyzing motion
step 3
For example, in one-dimensional motion, the datum could be the origin (0,0) of a coordinate system, from which distances and displacements are measured
step 4
In practical applications, the datum helps in setting initial conditions and simplifying the mathematical description of motion
Answer
A datum in kinematics is a reference point used to measure and describe motion.
Key Concept
Datum in Kinematics
Explanation
A datum is a fixed reference point used to define the position, velocity, and acceleration of an object in motion. It helps establish a coordinate system and simplifies the analysis of motion.
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