Are these half, double and triple identities correct or not? | Mathematics | Page 1

worn frost Oct 5, 2025, 10:39 AM

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I've noticed that there are many ways to express these identities

These identities are provided by my teacher in hurry so I am not sure if they're 100% correct or not

empty tigerBOT Oct 5, 2025, 10:39 AM

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hoary summit Oct 5, 2025, 11:47 AM

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All are correct except the second triple angle identity

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This is the correct one
$\cos 3\theta = 4\cos^3\theta - 3\cos\theta$

#Are these half, double and triple identities correct or not?