If `cos alpha+cos beta=a*sin alpha+sin beta=b` and `alpha-beta=2 theta` then `(cos3 theta)/(cos theta)=`

Explanation

To solve the problem, we start with the equations given:

1. \( \cos \alpha + \cos \beta = a \sin \alpha + \sin \beta = b \)
2. \( \alpha - \beta = 2\theta \)

We need to find the value of \( \frac{\cos 3\theta}{\cos \theta} \).

### Step 1: Rewrite the equations using the angle difference identity
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