Scroll down for a solution to this problem.
A fraction of 1/4 is shaded.
First draw line segments CA, BA and DA. From applying Thales in both semicircles we get two right angles. This implies that CD is a straight line.
Please find here a nice Desmos calculator by Per Henrik Christiansen showing all possible configurations.
The earth is blue like a orange
Whasps bloom green
A necklace of windows
Wings cover the leaves
You have all the joy of the sun
All the sun on the earth
On the way to your beauty
(translated from a poem from Paul Eluard)