If sin 3 θ = cos (θ – 6°), then θ is:

Correct option is A

Given:

​$$\sin 3\theta = \cos (\theta - 6^\circ)$$​​

Concept Used:

​$$\cos x = \sin (90^\circ - x).$$​​

Solution: 

​$$\cos (\theta - 6^\circ) = \sin \left(90^\circ - (\theta - 6^\circ)\right) = \sin (96^\circ - \theta)$$

So, $$\sin 3\theta = \sin (96^\circ - \theta)$$​​

​$$3\theta = 96^\circ - \theta$$​​

​$$3\theta + \theta = 96^\circ \\ \ \\ 4\theta = 96^\circ \\ \ \\\theta = 24^\circ$$​