Question

Se senx = 3/4 e 0 < x < π/2, calcule cos(2x)

Answer 1

Resposta:

cos2x= -2/16, (eu acho)

Explicação passo-a-passo:

cos (x+x)= cosx * cosx - senx* senx

cos2x=cos²x-sen²x, so que:

cos²x+sen²x=1

cos²x=1-sen²x

logo: Cos2x= 1-sen²x-sen²x

cos2x=1- 2sen²x ->cos2x=1-2*(3/4)²

cos2x=1-2*9/16

cos2x=1-18/16

cos2x=-2/16