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Explanation of expansion of Sin3A please.

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!
Reply 1
Avatar for Zacken
Zacken
22
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 sin⁡(A+B)≡sin⁡Acos⁡B+sin⁡Bcos⁡A\sin(A +B) \equiv \sin A \cos B + \sin B \cos A?
Reply 2
Avatar for Bysteven
Bysteven
OP
7
Yeah I have, this has just explained it, thanks very much mate.
Reply 3
Avatar for Zacken
Zacken
22
Original post by Bysteven
Yeah I have, this has just explained it, thanks very much mate.


You're very welcome.

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