Hi there,
Suffering from bit of a mental block here
Hoping someone can help!
I need to figure out how a step in a derivation from a textbook is done...basically, how exactly do you get to the point where you define the yellow area in the calotte-shaped area shown below as being equal to 2*pi*r *sin phi r d phi ? I presume that the 2*pi*r term arises from the circumference of the circle? The rest, I'm not so sure of...
Like I said, I've got a total mental block - I guess it's probably relatively straightforward!
Many thanks in advance!