Question

What is the formula for the surface area of revolution about the y-axis?

Answer 1

make x the subject.

Answer 2

\[2\pi\int_{a}^{b}x(y)\sqrt {1 + \left( {dx \over dy} \right)^2} dy\]

Answer 3

\[\int_a^b 2\pi y\ ds\] where ds is the arc length differential.

Answer 4

i am trying to find the surface area of a sphere

Answer 5

\[x^2+y^2=r^2\]\[x=\sqrt{r^2-y^2}\]\[y=\sqrt{r^2-x^2}\]

Answer 6

That results in kind of a nasty integral, better off using 4(pi)r^2 if you can

Answer 7

i know the result, i am trying to show the formula works