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If Sigma(r=1)^(n) cos^(-1)x(r)=0, then ...

If `Sigma_(r=1)^(n) cos^(-1)x_(r)=0, then Sigma_(r=1)^(n) x_(r)` equals

A

0

B

n

C

`(n(n+1))/(2)`

D

none of these

Text Solution

Verified by Experts

We know that
`0lecos^(-1)x_(r )lepi,r=1,2,.n`
`therefore underset(r=1)overset(n)Sigma cos^(-1) x_(r ) =0`
`rarr cos^(-1)x_(r ) =0 for r=1,2..n`
`rarr cos^(-1)x_(r)=0 for r=1,2..n`
`rarr x_(r ) =1 for r=1,2,…n `
`therefore underset(r=1)overset(n)Sigma x_(r )=underset(r=1)overset(n)Sigma1=n`
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OBJECTIVE RD SHARMA ENGLISH-INVERSE TRIGONOMETRIC FUNCTIONS -Section I - Solved Mcqs
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