Question

express the product 2cos5Acos3A as a sum

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Answer 1

Answer:

cos8A+cos2A

Step-by-step explanation:

2cos5Acos3A

=cos(5A+3A)+cos(5A-3A).

[2cosAcosB=cos(A+B)+cos(A-B)]

=cos8A+cos2A

Answer 2

SOLUTION

TO EXPRESS

The product 2cos5A cos3A as a sum

FORMULA TO BE IMPLEMENTED

We are aware of the formula of trigonometry that

2 cos A cos B = cos ( A + B ) + cos ( A - B )

EVALUATION

2 cos 5A cos 3A

= cos ( 5A + 3A ) + cos ( 5A - 3A )

= cos 8A + cos 2A

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