In an A.P., if `p^(t h)`term is `1/q`and `q^(t h)`term is `1/p`, prove that the sum of first pq terms is `1/2(p q+1),`where `p!=q`.

Explanation

To solve the problem, we start by using the properties of an arithmetic progression (A.P.).

### Step-by-step Solution:

1. **Define the terms of the A.P.**:
Let the first term of the A.P. be \( A \) and the common difference be \( D \).

2. **Express the P-th and Q-th terms**:
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