Chapter 6: Applications of Double Integration
Section 6.2: Volume
Example 6.2.7
If F=2−y−1/22 and R is the region bounded by the graphs of 1, cosx, and y=x on 0≤x≤1, calculate the volume of the region bounded above by the surface z=Fx,y and below by the plane z=0.
See Example 6.1.7.
Solution
Mathematical Solution
The region whose volume is to be computed is shown in Figure 6.2.7(a). The simplest iteration of the double integral that gives this volume takes the integrand as F and uses the order dx dy, with Q≐0.74:
∫Q1∫arccosyyF dx dy = 0.1812403381
If the order of integration is taken as dy dx, then the iterated integral would be the more tedious
∫0Q∫cosx1F dy dx+∫Q1∫x1F dy dx = 0.1812403381
Figure 6.2.7(a) The volume to be computed
Maple Solution - Interactive
Initialize
Tools≻Load Package: Student Multivariate Calculus
Loading Student:-MultivariateCalculus
Context Panel: Assign Name
F=2−y−1/22→assign
XL=arccosy→assign
Solve cosx=x for Q
Write the equation cosx=x.
Context Panel: Solve≻Numerically Solve
Context Panel: Assign to a Name≻Q
cosx=x→solve0.7390851332→assign to a nameQ
Access the MultiInt command via the Context Panel
Write F, the name of the integrand. Context Panel: Evaluate and Display Inline
Context Panel: Student Multivariate Calculus≻Integrate≻Iterated Fill in both panes (see Figures 5.3.(1, 2)) and select "integral" for the Output
Context Panel: Evaluate Integral
F = 2−y−122→MultiInt∫0.73908513321∫arccos⁡yy2−y−122ⅆxⅆy=0.1812403381
Iterate in the order dx dy via the template in the Calculus palette
Calculus palette: Iterated double-integral template
Context Panel: Evaluate and Display Inline
∫Q1∫arccosyyF ⅆx ⅆy = 0.1812403381
Iterate in the order dy dx via the template in the Calculus palette
∫0Q∫cosx1F ⅆy ⅆx+∫Q1∫x1F ⅆy ⅆx = 0.1812403381
The task template in Table 6.2.7(a) iterates in the order dx dy. The right-pointing arrow in the left-hand graph indicates that the inner (first) integration is in the x-direction. The right-hand image contains a graph of the region whose volume is computed by the integral.
Tools≻Tasks≻Browse:
Calculus - Multivariate≻Integration≻Visualizing Regions of Integration≻Cartesian 2-D
Evaluate ∬RΨx,y dA and Graph R
Area Element dA
Select dAdy dxdx dy
, Ψ=
Value of Integral
G=
b=
g=
a=
Bounding Curves
"Volume"
Table 6.2.7(a) Iteration in the order dx dy via visualization task-template
Each graph in Table 6.2.7(a) has had constrained scaling imposed.
Maple Solution - Coded
Install the Student MultivariateCalculus package.
withStudent:-MultivariateCalculus:
Define the integrand F.
F≔2−y−1/22:
Calculate the value of Q
Use the fsolve command for a numeric solution.
Q≔fsolvex=cosx,x
0.7390851332
Top-level, using the Int and int commands
IntF,x=arccosy..y,y=Q..1=intF,x=arccosy..y,y=Q..1
∫0.73908513321∫arccos⁡yy2−y−122ⅆxⅆy=0.1812403381
IntF,y=cosx..1,x=0..Q+IntF,y=x..1,x=Q..1=intF,y=cosx..1,x=0..Q+intF,y=x..1,x=Q..1
∫00.7390851332∫cos⁡x12−y−122ⅆyⅆx+∫0.73908513321∫x12−y−122ⅆyⅆx=0.1812403381
Use the MultiInt command from the Student MultivariateCalculus package
MultiIntF,x=arccosy..y,y=Q..1 = 0.1812403381
MultiIntF,x=arccosy..y,y=Q..1,output=integral
∫0.73908513321∫arccos⁡yy2−y−122ⅆxⅆy
MultiIntF,x=arccosy..y,y=Q..1,output=steps
0.1812403381
Use the MultiInt command with a pre-defined domain option
MultiIntF,y,x=RegionQ..1,arccosy..y = 0.1812403381
MultiIntF,y,x=RegionQ..1,arccosy..y,output=integral
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