what is the diameter of small semicircle?

a small semicircle is inscribed in a large semicircle.
the question is to find the diameter of a small semicircle.
to solve the problem, we must set up an equation that includes the radius.
we must apply the properties of a circle and the pythagorean theorem.
this video shows how to find the radius by using those mathematics, especially the property of a tangent to a circle. (made with vrew)
#diameter #pythagoreantherorem #circlegeometry