This problem is very similar:

https://www.quora.com/A-point-P-is-given-on-the-circumference-of-a-circle-of-radius-R-The-chord-QR-is-parallel-to-the-tangent-at-P-What-is-the-maximum-possible-area-of-a-triangle-PQR

See if that helps you

Thank you so much!

Can you help me solve the other problem I posted about the 52 cards?

The way you solved it was really easy to understand! Wow!

This link might help:

https://www.quora.com/Three-balls-are-drawn-without-replacement-from-a-bag-containing-3-black-5-purple-and-6-yellow-balls-Given-that-the-drawn-balls-are-all-the-same-colour-what-is-the-probability-they-are-purple