We are given a circle with a triangle inscribed in it. One side of the triangle is a diameter of the circle. We need to find the measure of the angle $x$ opposite to the diameter.

1. Problem Description

We are given a circle with a triangle inscribed in it. One side of the triangle is a diameter of the circle. We need to find the measure of the angle $x$ opposite to the diameter.

2. Solution Steps

Since one side of the triangle is a diameter of the circle, the triangle is a right triangle. The angle opposite the diameter is the right angle.

Therefore, $x = 90^{\circ}$.

3. Final Answer

$x = 90$