How Does Substitution Simplify the Gamma Function Integral?

matematikuvol
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\Gamma(x)=\int^{\infty}_0t^{x-1}e^{-t}dt

\Gamma(\frac{1}{2})=\int^{\infty}_0\frac{e^{-t}}{\sqrt{t}}dt=

take t=x^2

dt=2xdx

x=\sqrt{t}

=\int^{\infty}_0\frac{e^{-x^2}}{x}2xdx

Why here we can here reducing integrand by x?
 
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What is your question? You've done the substitution correctly, so you see how the x's cancel. What is the problem?
 
Lower limit is 0. Why I may cancel x's?
 
Because the functions are defined on intervals not containing the point 0, that's why you can have the x in the denominator and simplify it through.
 
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