I realized that following is apparently true: we had definitions of sine, cosine, etc. for angles of right triangle. Then, one suddenly draws X and Y axes, incorporates negative numbers, and sees that something is working well – incorporation of the negative sign to encode angles > 90. One then decides to forget about right triangle, be happy with negative numbers and all the beautiful (or "beautiful" when the juggling gets discovered) trigonometric equations that can be obtained this way. Am I right, this is how sine and cosine, etc. have been derived for obtuse angle?
2026-03-28 22:53:33.1774738413
Defining trigonometric functions for obtuse angle
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