answer of the exercice about sangaku

To draw this sangaku, you have to draw a semi-circle. Next, draw a triangle in this semi-circle. Next, draw a rectangle in this triangle. With this, you have three right triangle. And to find the circle in the triangle, you have to draw the bisector of this triangle and you have the center of the circle.
It was very easy, isn’t it ???

For the length, you could take every length.