A theorem from geometry states that if a triangle is inscribed in a circle such that one

Question:

A theorem from geometry states that if a triangle is inscribed in a circle such that one side of the triangle is a diameter of the circle, then the triangle is a right triangle. Show that this theorem is true for the circle x2 + y2 = 100 and the triangle formed by the lines y - 0, y = 1/2 x + 5 and y = -2x + 20.