What is Trigonometry? Who is responsible for right triangle trig? Is there one person who is credited for this?

I teach trigonometry in the geometry setting, using right triangles for our basis. But who discovered these relationships? Was there one person who can take the credit? What information is there about this?
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Who is this Pythagoras??

After just a little searching, I found out the Pythagoras and his students had a significant impact on our mathematical knowledge!
He was born on Samos, a Greek island in the Aegean Sea that is very close to the west coast of Turkey 580 B.C.
A major belief of his is "All is number". This means that numbers did not just exist as an abstraction or thought in the human mind BUT had a reality all their own that did not depend on one's mind. It meant that numbers and relations between numbers formed the basic core out of which everything else came. "Numbers were to Pythagoreus and his followers what atoms are to the human race today.
Can you find information about Pythagoras and his findings about music??

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Did you know Pythagoras founded the Order of the Pythagoreans? almost like a religion or cult? Can you tell me more?

What other contributions to mathematics are attributed to Pythagoras and his followers?