Posted by Chris Math Hw Help on .
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

Precalc/Calc 
Steve,
Looks like D to me.
sin u + sin v = 2 sin(½(u+v)) cos(½(u−v))