Question

Sec^2x+2sec=0. solve the equation for 0

Answer 1

u = sec x ( substitution )
u² + 2 u = 0
u ( u + 2 ) = 0
u = 0, or u = - 2
1/cos x = 0 1/cos x = - 2
(not accepted ) cos x = -1/2
x 1 = 2π/3, x 2 = 4π/3