Question

Решение пж и по быстрей

Answer 1

Sin²α + Cos²α = 1
Cos²α = 1 - Sin²α = 1 - 81/1681 = 1600/1681 , ⇒ Сosα = - 40/41
Sin2α = 2SinαCosα = 2*9/41*(-40/41) = -720/1681
Сos2α = 1 - 2Sin²α = 1 - 2*81/1681 = 1 - 162/1681 = 15/1681
tgα= Sinα/Cosα = 9/41: (-40/41) = -9/40
tg2α = 2tgα/(1 - tg²α) = 2*(-9/40)/(1 - 81/1600) = -9/20/1519/1600=-720/1519
Сtg2α = - 1519/720