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# Explanation of expansion of Sin3A please.

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1. So I am told Sin3A...
= Sin (2A + A)
= Sin2ACosA + Cos2ASinA.

Given the fact Sin2A = 2SinAcosA I can't get my head around this,
can someone please explain the expansion step by step.?

Thanks in advance!
2. (Original post by Bysteven)
So I am told Sin3A...
= Sin (2A + A)
= Sin2ACosA + Cos2ASinA.

Given the fact Sin2A = 2SinAcosA I can't get my head around this,
can someone please explain the expansion step by step.?

Thanks in advance!
Have you learnt ?
3. Yeah I have, this has just explained it, thanks very much mate.
4. (Original post by Bysteven)
Yeah I have, this has just explained it, thanks very much mate.
You're very welcome.

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