Could someone explain me how to go from blue to red? I've tried to do the triple integral integrating first for dphi and dalpha from 0 to 2phi and to 0 to phi? But I end up getting 2·phi^2 instead of 4phi
please help
OP here, I actually forgot the sin(o) when I integrated, I did it and I got 0, now I'm totally lost
>>7728460
I have no idea why you're talking about phi and alpha instead of phi and theta. But you integrate phi from 0 to 2pi and theta from 0 to pi.
>>7728479
It's spherical coordinates, no? Doesn't the phi go from 0 to pi and theta (or alpha?) from 0 to 2 pi?
>what is the solid angle of a sphere
>>7728606
>phi go from 0 to pi and theta (or alpha?) from 0 to 2 pi?
Math books and physics books swap them around. Whatever involves the sine goes from 0 to π and the other goes from 0 to 2π
the integral of sin theta = -cos theta from 0 to pi, so you get 2.
the integral from 1 from 0 to 2pi is 2pi.
therfore: 2*2pi=4pi. ez.
>>7728606
the sin theta says which is which.
