Question

22(sin²72°-cos²72°)/cos144°

Answer 1

$frac{22(sin^272^o-cos^272^o)}{cos144^o}frac{-22(cos^272^o-sin^272^o)}{}=\=frac{-22(cos(2*72^o))}{cos144^o}=frac{-22cos144^o}{cos144^o}=-22$
Формула cos2a=cos²a-sin²a