Can you find the radius of a semicircle or not?

well, a radius is only part of the full circle, but lets say have a semicircle and you know the length of the straight edge, you can divide that by 2 and get the radius of the full circle.

The radius of the semicircle is the same as the radius of a full circle. It is the line that cuts the circle in half, only half of it. You can find the circumference, too. Simply do the normal operation but divide by 2, because it is half of a circle.