Question

Упростите выражение:
(1-sin a)(1+sin a)/cos²(-a), a≠π/2+πn, n€Z.

Answer 1

$\frac{(1-Sin \alpha)(1+Sin \alpha ) }{Cos ^{2}(- \alpha ) } = \frac{1-Sin ^{2} \alpha }{Cos ^{2} \alpha } = \frac{Cos ^{2} \alpha }{Cos ^{2} \alpha }=1$