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Question #33ab5

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Dec 20, 2016

$RHS=sin7theta+sin4theta-sin2theta+sintheta$

$=(sin7theta+sintheta)+(sin4theta-sin2theta)$

$=(2sin4thetacos3theta)+(2cos3thetasintheta)$

$=2(sin4theta+sintheta)cos3theta$

$=4sin((5theta)/2)cos((3theta)/2)cos3theta=LHS$

Proved

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