Which of the following is a true statement regarding an isosceles triangle formed by two radii?

An isosceles triangle is defined by having at least two sides that are equal, which is exactly the case for the triangle formed by two radii of a circle. In this context, the two equal sides are the radii, while the third side, known as the base, is not necessarily the same length. The property of isosceles triangles also includes having two equal angles, which are the angles opposite the equal sides. Therefore, the statement that only two sides are equal accurately reflects the nature of this triangle.

The other options do not describe characteristics of the isosceles triangle accurately. All sides being equal would indicate that the triangle is equilateral, which is not the situation with just two equal sides. The base angles being different contradicts the fundamental property of an isosceles triangle, as the angles opposite the equal sides are always equal. Lastly, the angles being complementary refers to two angles that add up to 90 degrees, which does not apply to the angles of an isosceles triangle formed by radii, as they can sum to more than that depending on the triangle's dimensions.