# Surface area of Revolution

Jbreezy

## Homework Statement

I want the surface area of Revolution about x from [-2,2] of y = |x|
So I want to know if I can take it x from [0,2] and just multiply this result by 2?

## The Attempt at a Solution

Set up
dy/dx = (5/(2√x))

S = 2 ∏ ∫ 5x^1/2(√ 1 +((5/(2√x))^2)

from x = 0 , to x = 2. Then multiply this result by 2? Is this OK to do?

Homework Helper

## Homework Statement

I want the surface area of Revolution about x from [-2,2] of y = |x|
So I want to know if I can take it x from [0,2] and just multiply this result by 2?

## The Attempt at a Solution

Set up
dy/dx = (5/(2√x))

S = 2 ∏ ∫ 5x^1/2(√ 1 +((5/(2√x))^2)

from x = 0 , to x = 2. Then multiply this result by 2? Is this OK to do?

Yes, the function y=|x| is symmetric around the y-axis, so you can double the result from [0,2]. But why do you think dy/dx = (5/(2√x))??

Jbreezy
Because I;m tired lol and looked off the wrong sheet. My bad. I had this problem done I just didn't know if I could do what I said I didn't see why not though. Thanks,
Later