Trig identity proofs: cos(A+B) = cosAcosB - sinAsinB

836 views · Published 3 December 2014 · 12:32 · Indexed 4 November 2026

Channel: Magic Monk · 2014 · Education

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In this series of videos I will prove every single trigonometric identity. If you have any that you want to see the proof of, feel free to e-mail me. I suggest starting from the beginning so if you are stuck watching this video, go back to some earlier ones (e.g. the proof of sin(A+B) is here https://www.youtube.com/watch?v=mO-2D-L4yc8)

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