The angle in a semi-circle is a right angle.

Explanation

To prove that the angle in a semicircle is a right angle, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Circle and Points**:
Let’s consider a circle with center O. We will take points P and Q on the circumference of the circle such that the line segment PQ is a diameter of the circle. Let R be any point on the circumference of the circle.

2. **Understand the Angles**:
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