Posted by pooja on Saturday, April 30, 2011 at 7:53am.
Expand both sides using sum of angles formula:
cos(a+b)=cos(a)cos(b)-sin(a)sin(b)
cos(a-b)=cos(a)cos(b)+sin(a)sin(b)
Divide by cos(a) on both sides and solve for tan(a) to get:
tan(a)=cot(b)*(1-m)/(1+m)
Check me.