Question

identidades trigonometricas

cos2X=(1+senX)(1-senX)

Answer 1

cos(2x) = (1 + sen(x) ) (1 - sen(x) )
cos^2(x) - sen^2(x) = 1 - sen^2(x)
cos^2(x) = 1
x = 0 +  2k(pi)