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If cos alpha+ cos beta= a, sin alpha+ si...

If `cos alpha+ cos beta= a, sin alpha+ sin beta= b and alpha- beta= 2 theta`. Then `(cos 3 theta)/(cos theta)=`

A

`a^(2) + b^(2) - 2`

B

`a^(2) + b^(2) - 3`

C

`3 - a^(2) - b^(2)`

D

`(a^(2) + b^(2))//4`

Text Solution

Verified by Experts

The correct Answer is:
B
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