kill(all)$ load(atrig1)$ load(ntrig)$

Van = facebook.com/LearningCalculus;

f(x,y):=sin(x)*cos(y)-(1/2);

g(x,y):=tan(x)*cot(y)-1;

error(x,y):=f(x,y)-g(x,y);

error(%pi/4,%pi/4);

error(%pi*(3/4),-%pi/4);