Cos3+2cos5+cos7/cos+2cos3+cos5=cos5/cos3
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Step-by-step explanation:
LHS
cos7+cos3+2cos5/cos5+cos1+2cos3
=2cos(7+3/2)cos(7-3/2)+2cos5/ 2cos(5+1/2)cos(5-1/2)+2cos3
=2cos5cos2+2cos5/2cos3cos2+2cos3
=2cos5(cos2+1)/2cos3(cos2+1)
=cos5/cos3
RHS
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