Stuck on a problem!

1. Jan 30, 2005

NINHARDCOREFAN

The problem is:
Find the area of the surface of revolution generated by revolving the curve
e^(8θ), 0≤θ≥½π around the y-axis.

θ= Theta
½π= 1/2*pi
sqrt= sqare root
² = squared

Here's my work:
ds = sqrt( (e^(8θ))² + (e^(8θ))² )dθ
dθ = (e^(8θ)sqrt(2)
x = rcos(θ)= e^(8θ)cos(θ)
A = 2*½π*sqrt(2)*integral of (e^(16θ)cos(θ)) between 0 and ½π
I solved the integral and I got
2*½π*(2)/257*(e^(8θ)-16))

When I plugged the answer online, I got it wrong. Can someone please figure out what's wrong?

Last edited: Jan 31, 2005