Need your help now please; the assignment is due tonight and this is the last problem I am having trouble with. The red box is the value I keep getting wrong

The region R is bounded by the x-axis, the straight line in the graph and the vertical line x=2.

Need your help now please the assignment is due tonight and this is the last problem I am having trouble with The red box is the value I keep getting wrong The class=

Respuesta :

The volume of the region R bounded by the x-axis is: [tex]\mathbf{\iint_R(x^2+y^2)dA = \int ^{tan^{-1}(4)}_{0} \int^{\frac{2}{cos \theta}}_{0} \ r^3 dr d\theta}[/tex]

What is the volume of the solid (R) on the X-axis?

If the axis of revolution is the boundary of the plane region and the cross-sections are parallel to the line of revolution, we may use the polar coordinate approach to calculate the volume of the solid.

From the given graph:

The given straight line passes through two points (0,0) and (2,8). Thus, the equation of the straight line becomes:

[tex]\mathbf{y-y_1 = \dfrac{y_2-y_1}{x_2-x_1}(x-x_1)}[/tex]

here:

  • (x₁, y₁) and (xā‚‚, yā‚‚) are two points on the straight line

Suppose we assign (x₁, y₁) = (0, 0) and (xā‚‚, yā‚‚) = (2, 8) Ā from the graph, we have:

[tex]\mathbf{y-0 = \dfrac{8-0}{2-0}(x-0)}[/tex]

y = 4x

Now, our region bounded by the three lines are:

  • y = 0
  • x = 2
  • y = 4x

Similarly, the change in polar coordinates is:

  • x = rcosĪø,
  • y = rsinĪø

where;

  • x² + y² = r² Ā and dA = rdrdĪø

Therefore;

  • rsinĪø = 0 Ā  i.e. Ā r = 0 or Īø = 0
  • rcosĪø = 2 i.e. Ā  r Ā = 2/cosĪø
  • rsinĪø = 4(rcosĪø)  ⇒ tan Īø = 4; Ā Īø = tan⁻¹ (4)

  • ⇒ r = 0 Ā  to Ā  r = 2/cosĪø
  • Ā  Ā Īø = 0 Ā to Ā  Ā Īø = tan⁻¹ (4)

Then:

[tex]\mathbf{\iint_R(x^2+y^2)dA = \int ^{tan^{-1}(4)}_{0} \int^{\frac{2}{cos \theta}}_{0} \ r^2 (rdr d\theta )}[/tex]

[tex]\mathbf{\iint_R(x^2+y^2)dA = \int ^{tan^{-1}(4)}_{0} \int^{\frac{2}{cos \theta}}_{0} \ r^3 dr d\theta}[/tex]

Learn more about the determining the volume of solids bounded by region R here:

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