Question

Hi
this is part of integral i cant understand why
x=e^t
http://i42.tinypic.com/2ikdu1e.jpg

Answer 1

it used to substitute x at the end

Answer 2

you want to convert the integral so its with respect to t instead of x

this means you want to completely eliminate any x
because if when you're integrating with respect to t, you cant integrate any terms with x,
this is why you need to use substitution to change it to e^t

now, in order to get x=e^t
you start with your original t substitution or i usually use "u"

t= ln x
e^t = e^(ln x)= x

Answer 3

which part are you finding most confusing @aras ?