tan A/2 = (1-cosA)/sinA
So, you have
(1-cosA)/sinA = 1/sinA-sinA = (1-sin^2A)/sinA = cos^2A/sinA
so
cos^2A+cosA-1 = 0
Solve that for cosA, and then use the fact that
cos36° = (1+√5)/4
to prove the result
if tan A/2 =cosecA-sin A then prove cos^2
A/2=cos 36 degree
2 answers
That is negetive and posetive