kill(all)$

Van = facebook.com/LearningCalculus/2015;

load(ntrig)$ load(atrig1)$

degToRad(u):= u*%pi/180;

Cot(degToRad(150))=Cot(degToRad(40))-csc(degToRad(20));

final:subst(cot,Cot,%)$

float(lhs(final)) = float(rhs(final));