Найти 50cos²α, если tgα=7

1+ tg ^2 x = 1/ cos^2 x1+7 = 1/ 50cos^ x 8= 1/ 50 cos^ x8* 50 cos^2 x =1400 cos^ x =1cos^2 x = 1/400cosx =1/20cos x = 0.05