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Find the values of the following trigono...

Find the values of the following trigonometric ratio: `cos 855^0`

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`cos 855^o`
`= cos(5 xx 180^o -45^o)`
`= -cos 45^o`
`= -1 // sqrt 2`
As `855^0` is in 2nd quadrant So, cos is negative.
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RD SHARMA-TRIGONOMETRIC FUNCTIONS-Solved Examples And Exercises
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  2. Find the values of the following trigonometric ratio: cos570^@

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  3. Find the values of the following trigonometric ratio: cos 855^0

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  4. Find the values of the following trigonometric ratio: "sin"(-330^@)

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  7. Prove that: sin(8pi)/3cos(23pi)/6+cos(13pi)/3sin(35pi)/6=1/2

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  8. Prove that: cos 24^0+cos55^0+cos 125^0+cos 204^@+cos 300^0=1/2

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  9. Prove that: tan(-225^0)cot(-405^0)-tan(-765^0)cot(675^0)=0

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  10. Prove that:cos 570^0sin510^0+sin(-330^0)cos(-390^0)=0

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  14. In a Delta(ABC) prove that cos(("A"+"B")/2)=sin"C"/2dot

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  15. In a "DeltaA B C prove that tan(("A"+"B")/2)=cot("C"/2)

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