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14 votes
14 votes
Anyone help me please


2 \sin7 \alpha. \cos2 \alpha = \sin9 \alpha + \sin5 \alpha


User Alex Hinton
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1 Answer

17 votes
17 votes

Solution,

As we have,

⇒2SinACosB=Sin(A+B)+Sin(A-B)

Now,


2sin7\alpha .cos2\alpha =sin9\alpha +sin5\alpha \\\\LHS=2sin7\alpha .cos2\alpha \\\\LHS=sin(7\alpha +2\alpha )+sin (7\alpha -2\alpha )\\\\LHS=sin9\alpha +sin5\alpha

Hence, LHS=RHS

User Wutz
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