- #1
Saitama
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Homework Statement
Suppose [tex]sin^3xsin3x=\sum^n_{m=0}{}^nC_mcosmx[/tex] is an identity in x, where C0, C1, ...Cn are constants, and Cn [itex]\neq[/itex]0, then what is the value of n?
Homework Equations
The Attempt at a Solution
I expanded the sigma notation and got:-
[tex]sin^3xsin3x={}^nC_0cos0+{}^nC_1cosx+{}^nC_2cos2x...[/tex]
I wasn't able to think what should i do next?
Please help!
Thanks!