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Pre-calc/Calc

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Which expression is equivalent to sin(3x) + sin x?

A.
2cos(2x)sin x

B.
2sin(2x)sin x

C.
-2sin(2x)cos x

D.
2sin(2x)cos x

E.
-2cos(2x)sin x

  • Pre-calc/Calc -

    Looks like D to me.

    sin u + sin v = 2 sin(½(u+v)) cos(½(u−v))

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