Semicircles

Here : https://web2.0calc.com/questions/semicircles_5

Find the radius of the circle.

$(1+r)^2=1^2+(2-r)^2\\ 1+2r+r^2=1+4-4r+r^2\\ 6r=4\\ \color{blue}r=\frac{2}{3}$

$\color{blue}The\ radius\ of\ the\ circle\ is\  \frac{2}{3}.$

 !