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September 4, 2015
Posted by **Dini** on Tuesday, November 2, 2010 at 5:13pm.

- trigonometry -
**bobpursley**, Tuesday, November 2, 2010 at 5:25pmI think I would use the sum formulas, changing sin3x to sin(2x+x) and cos3x to cos(2x+x), then gather terms.