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Prove that `(d)/(dx)(cot^(-1)x)=(-1)/((1+x^(2)))`, where `x in R`. |
Answer» Let `y=cot(-1)x`, where `x in R and y in [0,pi]`. Then, `x=cot y` `rArr(dx)/(dy)=-"cosec"^(2)y=-(1+cot^(2)y)=-(1+x^(2))` `rArr(dy)/(dx)=(-1)/((1+x^(2))).` ltbr. Hence, `(d)/(dx)(cot^(-1)x)=(-1)/((1+x^(2))).` |
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