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The expression (cos6x+6cos4x+15cos2x+10...

The expression `(cos6x+6cos4x+15cos2x+10)/(cos5x+5cos3x+10cosx)` is equal to

A

`cos^(2)x`

B

`1+cosx`

C

`cos 2x`

D

`2cos x`

Text Solution

Verified by Experts

The correct Answer is:
D
We have,
`(cos6x+6cos4x+15cos2x+10)/(cos5x+5cos3x+10cosx)`
`=((cos6x+cos4x)+5(cos4x+cos2x)+10(cos2x+1))/(cos5x+5cos3x+10cosx)`
`(2cos5xcosx+10cos 3xcosx+20cos^(2)x)/(cos5xcos3x+10cosx)=2cosx.`
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OBJECTIVE RD SHARMA-TRIGONOMETRIC RATIOS AND IDENTITIES-Section I - Solved Mcqs
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