Question
Given that ( sin left[cot ^{-1}(x+1)right]=cos left(tan ^{-1} xright) ldots(1) )
We know that,
( cot ^{-1} A=sin ^{-1} frac{1}{sqrt{1+A^{2}}} )
Here, ( A=x+1 )
Applying this identity in equation ( (1), ) we have,
( sin left[sin ^{-1} frac{1}{sqrt{1+(1+x)^{2}}}right]=cos left(tan ^{-1} xright) ldots .(2) )
A/so we know that,
( tan ^{-1} A=cos ^{-1} frac{1}{sqrt{1+A^{2}}} )
Here, ( A=x ) Applying this identity in equation ( (2), ) we have, ( sin left[sin ^{-1} frac{1}{sqrt{1+(1+x)^{2}}}right]=cos left(cos ^{-1} frac{1}{sqrt{1+x^{2}}}right) )
( Rightarrow frac{1}{sqrt{1+(1+x)^{2}}}=frac{1}{sqrt{1+x^{2}}} )
Squaring and reciprocating both the sides, we have, ( 1+(1+x)^{2}=1+x^{2} )
( Rightarrow 1+1+x^{2}+2 x=1+x^{2} )
( Rightarrow 1+2 x=0 )
( Rightarrow x=frac{-1}{2} )

If sin(cot-'(x + 1) = cos(tan-' x), then x = (c) O (d)
Solution
