Question

dertemine o valor do cos x, sabendo que 3sen^2 x - 4sen x + 1 = 0 e que 0

Answer 1

 3sen^2x - 4sen x + 1 = 0

Fazendo y=sen x

 3y² - 4y+ 1 = 0

y'=[4+√(16-12)]/6=1
y'=[4-√(16-12)]/6=1/3

Se y=1=sen x
cos²x+sen²x=1
cos²x+1=1 ==>cos²x=0 ==>cos x=0


Se y=1/3=sen x 
cos²x+1/9=1
cos²x=8/9  ==>cos x=√(8/9)  ou cos x=-√(8/9)