If cos theta = 1/2 (a+(1)/(a)), then the...

If `cos theta = 1/2 (a+(1)/(a)),` then the value of `cos 3 theta ` is .............
A) `1/8 (a ^(3) +(1)/(a ^(3)))` B) `3/2 (a+(1)/(a))` C) `1/2 (a^(3) + (1)/(a^(3)))` D) `1/3 (a^(3) +(1)/(a ^(3)))`

A

`1/8 (a ^(3) +(1)/(a ^(3)))`

B

`3/2 (a+(1)/(a))`

C

`1/2 (a^(3) + (1)/(a^(3)))`

D

`1/3 (a^(3) +(1)/(a ^(3)))`

Verified by Experts

The correct Answer is:

C

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