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If cos28^0+sin28^0=k^3, t h e ncos17^0 i...

If `cos28^0+sin28^0=k^3, t h e ncos17^0` is equal to `(k^3)/(sqrt(2))` (b) `-(k^3)/(sqrt(2))` (c) `+-(k^3)/(sqrt(2))` (d) none of these

A

`(k^(3))/sqrt(2)`

B

`-(k^(3))/sqrt(2)`

C

`+-(k^(3))/sqrt(2)`

D

none of these.

Text Solution

Verified by Experts

The correct Answer is:
A
`cos17^(@)=cos(45^(@)-28^(@))`
`cos45^(@)cos28^(@)+sin45^(@)sin28^(@)`
`=(cos 28^(@)+sin 28^(@))/(sqrt(2))=(k^(3))/(sqrt(2))`
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