Math, asked by Mohitgear8630, 4 months ago

Prove
Cos7a+cosa=2cos4acos3a

Answers

Answered by Sajidalikp

1

Answer:

cosx+cosy=2cosx+y/2.cosx-y/2

cos7a+Cosa=2cos((7a+a)/2).cos((7a-a)/2)

=2cos8a/2.cos6a/2

=2cos4acos3a=Rhs

Answered by sindhussindhus61

3

cos 7a+cosa=2cos4acos3a

cosx+cosy=2cosx+y/2. cosx-y/2. cos7a+Cosa=2cos((7a+a)/2).cos((7a-a)/2) . =2cos8a/2.cos6a/2. =2cos4acos3a=Rhs.

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