If `cosx+cosy-cos(x+y)=3/2,` then (a)`x+y=0` (b) `x=2y` (c)`x=y` (d) `2x=y`

Explanation

To solve the equation \( \cos x + \cos y - \cos(x+y) = \frac{3}{2} \), we can follow these steps:

### Step 1: Use the Cosine Addition Formula
We start with the equation:
\[ \cos x + \cos y - \cos(x+y) = \frac{3}{2} \]
Using the cosine addition formula, we know that:
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