Home / AP Calculus AB : 8.11 Volume with Washer Method: Revolving  Around the x- or y-Axis- Exam Style questions with Answer- FRQ

AP Calculus AB : 8.11 Volume with Washer Method: Revolving  Around the x- or y-Axis- Exam Style questions with Answer- FRQ

Question

Let R and S be the regions in the first quadrant bounded by:

  • R: x-axis, y = 2 – x³, and y = tan x
  • S: y-axis, y = 2 – x³, and y = tan x

Intersection point: (0.902155, 1.265751)

(a) Find the area of R.

(b) Find the area of S.

(c) Find the volume when S is revolved about the x-axis.

▶️ Answer/Explanation

Solution

(a) Area of R:

Method 1: Vertical slices \[ \text{Area} = \int_0^A \tan x \, dx + \int_A^{2^{1/3}} (2 – x^3) \, dx \approx 0.729 \] where A ≈ 0.902155

Method 2: Horizontal slices \[ \text{Area} = \int_0^B [(2 – y)^{1/3} – \tan^{-1}y] \, dy \approx 0.729 \] where B ≈ 1.265751

(b) Area of S:

Method 1: Vertical slices \[ \text{Area} = \int_0^A (2 – x^3 – \tan x) \, dx \approx 1.160 \]

Method 2: Horizontal slices \[ \text{Area} = \int_0^B \tan^{-1}y \, dy + \int_B^2 (2 – y)^{1/3} \, dy \approx 1.160 \]

(c) Volume of revolution:

Using washer method: \[ V = \pi \int_0^A [(2 – x^3)^2 – \tan^2 x] \, dx \approx 2.652\pi \approx 8.331 \]

Scroll to Top