1.

The value of following is `cos24^(@)+cos55^(@)+cos125^(@)+cos204^(@)+cos300^(@)`A. `-1//2`B. `1//2`C. `2`D. `1`

Answer» Correct Answer - b
The value of `cos24^(@)+cos55^(@)+cos125^(@)+cos204^(@)+cos300^(@)`
We know that `cos(180^(@)+-theta)`
`=-cos theta`
`rArr cos24^(@)+cos55^(@)+cos(180^(@)-55^(@))+cos(180^(@)+24^(@))=cos(360^(@)-60^(@))`
`rArrcos24^(@)+cos55^(@)-cos55^(@)-cos24^(@)+cos60^(@)`
`rArrcos 60^(@)=(1)/(2)`


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