Mathematics
LatriciaShack
2016-09-21 03:51:21
Express cos7xcos2x in the form of A(cosBx+cosCx) where A,B and C are constants to be determined.
ANSWERS
MarianaG
2016-09-21 09:04:23

[latex]cos(7x+2x)=cos7xcos2x-sin7xsin2x[/latex] [latex]cos(7x-2x)=cos7xcos2x+sin7xsin2x[/latex] [latex]impliescos9x+cos5x=2cos7xcos2x[/latex] [latex]impliescos7xcos2x=dfrac12(cos9x+cos5x)[/latex] [latex]implies A=dfrac12,B=9,C=5[/latex]

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