Posted by **Jen** on Saturday, December 9, 2006 at 1:14pm.

A = 1/2 ab Sinè

How is dA/dt related to da/dt, db/dt and dè/dt

dA/dt= 1/2 b SinTheta da/dt + 1/2 a SinTheta db/dt + 1/2 ab cosTheta dTheta/dt

This is a U = xyz form

dU/dt= xy dz/dt + ...