please help me to express this

[ryan882]

By expressing sin 3A as sin(2A+A) find an expression for sin 3A in terms of sin A

 

[Deleted member 4993]

By expressing sin 3A as sin(2A+A) find an expression for sin 3A in terms of sin A

Use

Sin(A+B) = Sin(A)*Cos(B) + Sin(B)*Cos(A)............................(1)

then use

Sin(2A) = Sin(A+A) to express Sin(2A) in terms Sin(A) and Cos(A)

Then use Sin(3A) = Sin(2A+A) and Cos²(A) = 1 - Sin²(A) and Cos(2A) = 1 - 2*Sin²(A) to get your final result.

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