Question #13cfd

1 Answer
Jim G.
Jul 22, 2017

#2sin2xcos7y#

Explanation:

#"using the "color(blue)"addition formulae"#

#color(red)(bar(ul(|color(white)(2/2)color(black)(sin(A+-B)=sinAcosB+-cosAsinB)color(white)(2/2)|)))#

#sin(2x+7y)=sin2xcos7y+cos2xsin7y#

#sin(2x-7y)=sin2xcos7y-cos2xsin7y#

#rArrsin(2x+7y)+sin(2x-7y)=2sin2xcos7y#

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