integration analysis

This is a definite integral, so we need to find the area under the integrand f(p), which we do by using the Fundamental Theorem of Calculus: we find an antiderivative, evaluate it at the endpoints of the integral, and take the difference of the values.

To find an antiderivative of f(p), we go through our list of integration methods:

Recognize elementary antiderivatives
Rewrite the integrand to make it easier
Use substitution to reverse the chain rule or simplify the integrand
Use integration by parts
Use inspection to see the value of a definite integral

to find one that works for this integrand. In this case, only one method is appropriate. We can rewrite the integrand: use properties of exponents to combine the numerator and denominator of the fraction to give an expression that is more easily integrable. This is shown below.

Rewriting:
Use properties of exponents to combine the numerator and denominator of the fraction to rewrite the integral:

[ e^p / sqrt(e^p) ] = e^{(1/2) p}.

Thus,

[ e^p / sqrt(e^p) ] dp =

e^{(1/2) p}dp

which can be evaluated using substitution (of "ax"), to obtain

e^{(1/2) p}dp = (2 e^{(1/2) p}) + C.

Explanation for rewritten term(s)
Substitution (of "ax")
Let w = 1/2 p. Then w' = 1/2, so (1/(1/2)) dw = dp. The integral can therefore be rewritten as

e^{(1/2) p} dp =

e^w (1/(1/2)) dw = 2 e^w + C

Thus, substituting back for w,

e^{(1/2) p} dp = 2 e^{(1/2) p} + C

To evaluate the definite integral, we take this antiderivative, evaluate it at the endpoints of the integral (0 and ln(9)), and take the difference of the values. This gives

[ (2 e^{(1/2) (ln(9))}) ] - [ (2 e^{(1/2) (0)}) ] = 4.

integration tutorial: analysis