If cos θ = cos α then general solution for θ is:

Correct option is A

Given:

​$$\cos \theta = \cos \alpha$$

Solution:

​$$\theta = \alpha + 2n\pi$$​ comes from the cosine function being positive in the first and fourth quadrants.

​$$\theta = -\alpha + 2n\pi$$​ comes from the cosine function being positive in the second and third quadrants.

Thus, the general solution is:

​$$\theta = \alpha + 2n\pi \quad \text{or} \quad \theta = -\alpha + 2n\pi \quad \text{where} \, n \in \mathbb{Z}.$$

Thus, option (a) is right.