sin2a/(1+cos2a)=1/2
2sin2a-1=sqrt(1-sin^2(2a))
sin2a=t
(2t-1)^2=1-t^2
4t^2+1-4t=1-t^2
5t^2-4t=0
5t=4
t=4/5
(tg2a-1)/sin2a=(((2*0,5)/(1-1/4)-1))*(5/4)=(4/3-1)*(5/4)=5/12
sin2a/(1+cos2a)=1/2
2sin2a-1=sqrt(1-sin^2(2a))
sin2a=t
(2t-1)^2=1-t^2
4t^2+1-4t=1-t^2
5t^2-4t=0
5t=4
t=4/5
(tg2a-1)/sin2a=(((2*0,5)/(1-1/4)-1))*(5/4)=(4/3-1)*(5/4)=5/12