Question

证明sina=1+tan2分之2α分之2tan2分之α

Answer 1

(2tana/2)/(1+(tana/2)^2)=2(tana/2)*(cosa/2)^2/(1+(tana/2)^2)*(cosa/2)^2=2(sina/2cosa/2)/(sina/2^2+cosa/2^2)=sina/1=sina