Question

СРОЧНО РЕШИТЬ 8 , УМОЛЯЮ

Answer 1

$5-20sin^2 alpha cos^2 alpha =5-5sin^22 alpha =5cos^22 alpha \ \ if~~~ alpha = frac{pi}{12} ~~~ then~~~~ 5cos^22 alpha =5cos^2 frac{pi}{6}=5cdotbigg( dfrac{sqrt{3}}{2} bigg)^2= dfrac{15}{4}$