Question

2/соs^2 31 градуса + сos^2 121 градуса

Answer 1

$frac{2}{cos^2 31^o+cos^2 121^o}=\\frac{2}{cos^2 31^o+(cos (90^o+31^0))^2}=\\frac{2}{cos^2 31^o+(-sin 31^o)^2}=\\frac{2}{cos^2 31^0+sin^2 31^o}=frac{2}{1}=2$