Difference between revisions of "2cos(mt)cos(nt)=cos((m+n)t)+cos((m-n)t)"
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(Created page with "==Theorem== The following formula holds for $m,n \in \{0,1,2,\ldots\}$: $$2\cos(mt)\cos(nt)=\cos((m+n)t)+\cos((m-n)t),$$ where $\cos$ denotes cosine. ==Proof== ==Referen...") |
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Latest revision as of 22:07, 19 December 2017
Theorem
The following formula holds for $m,n \in \{0,1,2,\ldots\}$: $$2\cos(mt)\cos(nt)=\cos((m+n)t)+\cos((m-n)t),$$ where $\cos$ denotes cosine.
Proof
References
- 1978: T.S. Chihara: An Introduction to Orthogonal Polynomials ... (next) $(1.1)$
