Question

Smalleat positive angle satisfying the equation cos^2x+cos^2(2x)+cos^2(3x)=1

Answer 1

Step-by-step explanation:

HINT:

cos2(x)+cos2(2x)+cos2(3x)=1⟺

1+6cos2(x)−20cos4(x)+16cos6(x)=1⟺

Substitute y=cos2(x):

16y3−20y2+6y=0⟺

2y(2y−1)(4y−3)=0⟺

y(2y−1)(4y−3)=0