Question

The number of solution(s) for the equation 3cos theta-4cos^(3)theta =1 in theta in -pi pi is​

Answer 1

Step-by-step explanation:

cos3θ=4cosθcos(θ+x)cos(θ−x)

⇒4cos

3

θ−3cosθ=4cosθcos(θ+x)cos(θ−x)

⇒4cos

2

θ−3=4(cos

2

θ−sin

2

x)

⇒sin

2

x=

4

3

=(

2

3

)

2

=sin

2

3

π

⇒x=kπ±

3

π