1/2 (tantheta-cottheta)/(tantheta+cottheta+1)
(sintheta/costheta-costheta/sintheta)/(2(sintheta/costheta+costheta/sintheta+1)
((sin^2theta-cos^2theta)/(sinthetacostheta))/((2sin^2theta+2cos^2theta+2sinthetacostheta)/(sinthetacostheta))
((sin^2theta-cos^2theta)/(sinthetacostheta))xx((sinthetacostheta)/(2sin^2theta+2cos^2theta+2sinthetacostheta))
(sin^2theta-cos^2theta)/(2sin^2theta+2cos^2theta+2sinthetacostheta)
Recall that #sin^2x+cos^2x=1
(sin^2theta-cos^2theta)/(2+2sinthetacostheta)
Recall that cos(2x)=cos^2x-sin^2x=>-cos(2x)=sin^2x-cos^2x
-cos(2x)/(2+sin(2x))