Question

find the surface area of the function rotated about x axis for y=cosx

Answer 1

Is there bound on x

Answer 2

from x= 2 to 4

Answer 3

Okk i m on phone so I can't draw anything but

Answer 4

You have a radius varying across x and with respect to x axis so radius = cos x volume is pi r square varying x from 2 to 4

Answer 5

U got it? Ur adding all the parallel circle areas radius cos x where ur radius varies from x equal two to four

Answer 6

Integral of pi times cos x
Bounds x from 2 to 4

Answer 7

That shud be pi times cos x squared

Answer 8

i got it. Thanks!

Answer 9

why isn't it 2 pi?

Answer 10

i was taught as the integral of 2 pi

Answer 11

You have to see the picture here try to understand the formula look up the method of calculating volume through the method of circular disks