Check out this video by “patrickJMT”. His videos are excellent.
In this case, the reason why we can change the order of integration is Tonelli’s Theorem, since the integrand is non-negative.
How to Change Order of Integration
Check out this video by “patrickJMT”. His videos are excellent.
In this case, the reason why we can change the order of integration is Tonelli’s Theorem, since the integrand is non-negative.
Mathtuition88 