Question 782034
I'm using A for alpha and B for beta.<P>
cos (a-b) = cos(a)cos(b)+sin(a)sin(b)<P>
tan = sin/cos and cot=cos/sin<P>
{{{(cos(a)cos(b)+sin(a)sin(b))/sin(a)cos(b) = cos(a)cos(b)/sin(a)cos(b) + sin(a)sin(b)/sin(a)cos(b) = cot(a)*1 + 1*tan(b)= cot(a)+tan(b)}}}