Prove that: `sin^2B=sin^2A+sin^2(A-B)-2sin A cos B sin(A-B)`

Explanation

To prove that \( \sin^2 B = \sin^2 A + \sin^2 (A - B) - 2 \sin A \cos B \sin (A - B) \), we will start from the right-hand side (RHS) and manipulate it step by step.

### Step 1: Write down the RHS
We start with the right-hand side:
\[ \sin^2 A + \sin^2 (A - B) - 2 \sin A \cos B \sin (A - B) \]

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