A circle with four chords and a diameter. What’s the proportion blue : green?

Solution

Blue : green is 1 : 1.

This problem is widely known as the Butterfly Theorem. A staggering amount of 25 solutions can be found here.

Poem

Angel wings
Or butterfly theorem
He flies with a high speed dash
It’s an ephemeral life
Between heaven and earth
A flight among the flowers
That brings joy and happiness
Every day is party
Without being worked up
He masters the horizon
With his angel wings
The butterfly

Bella