Question

Вычислите без использования калькулятора Cos^2 150°/ 1+sin 210°

Answer 1

cos²150°/(1+sin210°)=cos²(π-30°)/(1+sin(π+30°)=(-cos30°)²/(1-sin30°)=
=cos²30°/(1-sin30°)=(√3/2)²/(1-1/2)=(3/4)/1/2=3/2;