Show that \frac{\sin(3x)}{\sin x}+\frac{\cos(3x)}{\cos x}=4\cos(2x)

Eileen Garza

Eileen Garza

Answered question

2022-05-03

Show that
sin(3x)sinx+cos(3x)cosx=4cos(2x)

Answer & Explanation

attefrimibeocx

attefrimibeocx

Beginner2022-05-04Added 14 answers

sin(3x)sinx+cos(3x)cosx
=sin(3x)cosx+cos(3x)sinxcosxsinx
=sin(3x+x)sinxcosx
=sin4xsinxcosx
=2sin2xcos2xsinxcosx
=4sinxcosxcos2xsinxcosx
=4cos2x

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