Proving d/dx[sin(x)] = cos(x)

The derivative of sin(x) is cos(x), proven rigorously using the limit definition, angle addition identity, and two standard trigonometric limits.


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Feynman technique

Learn with the Feynman Technique

Explain each idea in your own words in handwriting, then upload a photo for AI critique. Two attempts per question — there's no "right" answer, only depth of understanding.