### Eric Nicholas K's answer to Dunelm's Secondary 3 A Maths Singapore question.

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This is a rough idea on how to work this problem. If you forget the double angle formula, you can still split cos 2x into cos (x + x) in a similar way.

These are the dedicated formulae for sin 3x and cos 3x, but you do not have to memorise this at your level. JC students use the result for sin 3x and cos 3x more frequently than secondary students do.

These are the dedicated formulae for sin 3x and cos 3x, but you do not have to memorise this at your level. JC students use the result for sin 3x and cos 3x more frequently than secondary students do.

Date Posted:
5 months ago

Thank You