Question

How to find the solution of cost(x-1)=0 on the interval [0,2pi]I keep seeing cos(x)-1=0 but this isn't the same thing. Please help!

Answer 1

(5+4cosθ)(2cosθ+1)=0

⇒cosθ=−

4

5

(not possible) cosθ=−

2

1

⇒cosθ=−

2

1

⇒cosθ=−cos

3

π

=cos(π±

3

π

)

⇒θ=

3

2π

,

3

4π

(II and III quad, cosine is negaitve)p