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Which of the following is/are the value of `"cos"[1/2cos^(-1)(cos(-(14pi)/5)]?` (a)`cos(-(7pi)/5)` (b) `sin(pi/(10))` (c)`cos((2pi)/5)` (d) `-cos((3pi)/5)`

A

`cos(-(7pi)/(5))`

B

`sin((pi)/(10))`

C

`cos((2pi)/(5))`

D

`-cos((3pi)/(5))`

Text Solution

Verified by Experts

The correct Answer is:
B, C, D
`cos (-(14pi)/(5)) = cos.(14pi)/(5) = cos.(4pi)/(5)`
Hence, `cos.(1)/(2) cos^(-1) (cos.(4pi)/(5)) = cos.(2pi)/(5)`
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