# area of surface by rotating the curve

• May 3rd 2010, 05:10 PM
victorxz90044
area of surface by rotating the curve
Find the area of the surface generated by rotating the curve x=1 + t^2, y =t from t = 0 to t= 4 about the x-axis

can u show ur steps.... need to learn this for a test

thankx
• May 3rd 2010, 05:21 PM
skeeter
Quote:

Originally Posted by victorxz90044
Find the area of the surface generated by rotating the curve x=1 + t^2, y =t from t = 0 to t= 4 about the x-axis

can u show ur steps.... need to learn this for a test

thankx

$\displaystyle A = \int_{t_1}^{t_2} 2\pi \cdot r(t) \cdot \sqrt{[x'(t)]^2 + [y'(t)]^2} \, \, dt$
• May 3rd 2010, 05:28 PM
victorxz90044
detail
May you please give a little detail.... thank you for answering
• May 3rd 2010, 05:36 PM
skeeter
Quote:

Originally Posted by victorxz90044
May you please give a little detail.... thank you for answering

$\displaystyle r(t)$ = radius of revolution of the curve in terms of t

$\displaystyle \sqrt{[x'(t)]^2 + [y'(t)]}$ ... you should know what this represents.