25.A semicircle is inscribed in an isosceles triangle with base 16 and height 15 so that the diameter of the semicircle is contained in the base of the triangle as shown.What is the radius of the semicircle?( )
一個半圓內接于一個底邊為16,高為15的等腰三角形中,使得半圓的直徑包含在三角形的底邊上,如圖所示。這個半圓的半徑是多少?( ?。?/div>