Если αϵ(90, 180) и sinα= 12/13 . найдите cosα=? и tgα=?

sinα = 12/13 ; π/2 < α < π

sin^2 α + cos^2 α = 1

cos^2 α = 1 - sin^2 α

cos^2 α = 1 - 144/169 = 25/169

cosα = 5/13

cosα = -5/13 cosα = -5/13

π/2 < α < π

tgα = sinα/cosα = (12/13)/(-5/13) = 12/-5 = -2,4

ответ : -5/13 ; -2,4