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यदि (If) `y=cos^(-1)((x-x^(-1))/(x+x^(-1)))` (find) `(dy)/(dx)` ज्ञात करें ।

Answer» `y=cos^(-1)((x-(1)/(x))/(x+(1)/(x)))=cos^(-1)((x^(2)-1)/(x^(2)+1))`
`=cos^(-1)(-(1-x^(2))/(1+x^(2)))=cos^(-1)(-(1-tan^(2)theta)/(1+tan^(2)theta)),[x=tantheta` रखने पर ]
`=cos^(-1)(-cos2 theta)=cos^(-1)[cos(pi-2 theta)]`
या `y=pi-2 theta=pi-2tan^(-1)x`
`therefore(dy)/(dx)=-(2)/(1+x^(2))`


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