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If tan(A+B)=3 tan A , prove that (a) sin...

If `tan(A+B)=3 tan A` , prove that (a) `sin(2A+B)=2sin B`

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(a) `tan (A+B)=3tanA`
or `(sin(A+B)cosA)/(sinA cos(A+B))=3`
or `(sin(A+B)cosA+sinAcos(A+B))/(sin(A+B)cosA-tanAcos(A+B))=(3+1)/(3-1)`
or `(Sin(A+B+A))/(sin(A+B-A))=2`
or `sin(2A+B)=2sin B`. ltbr. `-4 sin B cos B`
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