1.

यदि `theta` एक धनात्मक न्यूनकोण है और `tan2theta.tan3theta=1` है तो `(2cos^(2)((5theta)/(2))-1)` का मान क्या होगा?A. `-(1)/(2)`B. `1`C. `0`D. `(1)/(2)`

Answer» Correct Answer - c
`tan2 theta tan 3theta=1`
`(2theta+2theta)=90^(@)`
`5theta=90^(@)`
(if `tanA.tanB=1`, then `A+B=90^(@)`)
`rArr[2cos^(2)(5theta)/(2)-1] `
`rArr2cos^(2)(90^(@))/(2)-1`
`rArr2cos^(2)45^(@)-1`
`rArr(2)/(2)-1`
`rArr1-1=0`


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