Unlocking Trig Identities: Proving sin(2x + pi/3)

[iamthegelo]

Homework Statement

By using trig formulas show that,

sin(2x + pi/3) = sin(2x) + sin(2(x+pi/3))

Homework Equations

Trig Identities

The Attempt at a Solution

I've used double angle formulas, sin(a+b) formulas, I just can't seem to get it.

 

[CompuChip]

It does look like a case for sin(a + b). Can you show us what went wrong when you simply apply the identity for sin(a + b) = sin(a) ... + ... to sin(2x + pi/3) ?

 

[lurflurf]

write (for the left hand side)
sin(2x + pi/3)=[sin(2x + pi/3)-sin(2x +2pi/3)]+sin(2(x + pi/3))
recall the identity for
sin(a)-sin(b)