double integral of f(x,y)dxdy in polar coordinates
2 answers
what is double integral (f(psi,theta)dTheta dpsi ?
Trouble is that length along circumference is r theta
so
a little area is r dtheta dr
so
we need (r dTheta) dr
or
integral f(r, theta) r dr dtheta
so
a little area is r dtheta dr
so
we need (r dTheta) dr
or
integral f(r, theta) r dr dtheta