Question

упростите выражение (1-sin a)(1+sin a)/cos^2(-a)

Answer 1

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