In any `DeltaABC, sum (b - c) cot `A/2`=

Options

A. 0
B. 1
C. `-1`
D. none of these

Explanation

To solve the problem, we need to show that in any triangle \( \Delta ABC \), the sum \( \sum (b - c) \cot \frac{A}{2} = 0 \).

### Step-by-Step Solution:

1. **Understand the Problem**: We need to prove that the sum of \( (b - c) \cot \frac{A}{2} \) for angles \( A, B, C \) in triangle \( ABC \) equals zero.

2. **Using the Sine Rule**: Recall the sine rule, which states:
\[
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