Problems on trigonometric identities and equations
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Prove this identity:
7. sin(x+y)/sin(x-y) = coty +cotx / coty - cot x
2 sinxcos³x - 2 sin³xcosx
9. If cosx=-1/4 and pie/2<x<pie, the cos (pie/6 - x) = ?
10. Prove this identity:
cos 8x = cos²4x - sin²4x.
Please see the attached file.
7. Prove: sin(x+y)/sin(x-y) = coty +cotx / coty - cot x
We start from right hand side:
. Hence proved.
8. Simplify: 2 sinxcos³x - 2 ...
Methods to simplify trigonometric expressions using simple and fundamental trigonometric identities are discussed.