this is a particular type of integrals.... even √tanxdx can be done in this way with some modifications....
then again for ∫x2dx/(x4+1) follows the same above rule with smple modifications.
I=∫(√tanx+√cotx)dx
let √tanx=t
dt = 1/(2√tanx)sec2x = {1+t4}/2t.dx
dx = 2t/(1+t4)dt
I=∫(√tanx+√cotx)dx
subst from above,
I=∫(t+1/t)2t/(1+t4)dt
I=∫2(t2+1)/(t4+1)dt
now, divide numerator and denominator by t2
I=∫2(1/t2+1)/(t2+1/t2)dt
I=∫2(1/t2+1)/{(t-1/t)2)+2}dt
Now, t-1/t = m
differentiating, (1+1/t)dt = dm
Subst in equation above...
I = ∫2/{m2+2}dm
I =2/√2. tan-1(m/√2)
I = √2 tan-1(m/√2)
Where m=√tan x-√cot x
this is a particular type of integrals.... even √tanxdx can be done in this way with some modifications....
then again for ∫x2dx/(x4+1) follows the same above rule with smple modifications.
wite the intefral as I=∫(sinx+cosx)/(sinx.cosx)1/2dx
Put sinx-cosx= t
and (sinx+cosx)dx=dt
2csox.sinx=1-t2
the given integral become
I=√2∫dt/(1-t2)1/2 = sin-1(t)+C
=sin-1(sinx-cosx)+c