Evaluate 
Let, x = tan t
Differentiating both side with respect to t
⇒ dx = sec2t dt
Again, let cos t = z
Differentiating both side with respect to t
⇒ -dz = sin t dt
Using formula 
and 
Again, put z = cos t = cos(tan-1x)
1
Evaluate
Let, x = tan t
Differentiating both side with respect to t
⇒ dx = sec2t dt
Again, let cos t = z
Differentiating both side with respect to t
⇒ -dz = sin t dt
Using formula and
Again, put z = cos t = cos(tan-1x)