Integration: Rationalizing and then Partial Fractions

In summary, the given integral can be simplified to \int\frac{cos(log_7(u))}{(u)ln(7)}du by letting u=ex+9 and du=exdx. Then, by letting t=\log_7 u, the integral can be further reduced to a constant times the integral of cosine. The solution may then involve using log rules, splitting the integral into two separate integrals, and applying partial fractions.
  • #1
mickellowery
69
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Homework Statement


[tex]\int[/tex][tex]\frac{e^xcos(log_7(e^x+9))}{(e^x+9)ln(7)}[/tex]dx


Homework Equations





The Attempt at a Solution


Let u= (ex+9)
du= exdx
New integral [tex]\int[/tex][tex]\frac{cos(log_7(u))}{(u)ln(7)}[/tex]du
This is where I got l little lost. Should I let log7(u)=[tex]\frac{ln(u)}{ln(7)}[/tex]? Or is this just a waste of time. I was thinking after that I would use log rules to make it ln(u)-ln(7) and then split it into two separate integrals and follow that by partial fractions. I'm just curious if I'm on the right track.
 
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  • #2
Just let [tex]t=\log_7 u[/tex]. Then only constant times integral of cosine is left.
 

FAQ: Integration: Rationalizing and then Partial Fractions

What is integration?

Integration is a mathematical process that involves finding the area under a curve or the accumulation of a function. It is the inverse operation of differentiation and is used to solve various real-world problems in fields such as physics, engineering, and economics.

What is rationalizing?

Rationalizing is the process of eliminating irrational numbers, such as square roots, from the denominator of a fraction. This is done by multiplying both the numerator and denominator by the conjugate of the irrational number. This is often done in integration to make the integration process easier.

What is partial fractions?

Partial fractions is a method used to break down a complex fraction into smaller, simpler fractions. This is done by decomposing the original fraction into its constituent parts, which can be integrated separately. Partial fractions are often used in integration when the original function cannot be integrated directly.

Why is it important to rationalize and use partial fractions in integration?

Rationalizing and using partial fractions can make the integration process more manageable. By breaking down a complex fraction into simpler fractions, the integration can be done more efficiently. Rationalizing also helps to avoid dealing with imaginary numbers, which can complicate the integration process.

What are some common strategies for rationalizing and using partial fractions in integration?

Some common strategies for rationalizing and using partial fractions in integration include identifying the type of fraction (proper, improper, complex), finding the appropriate substitution, using algebraic manipulation to simplify the fraction, and applying the appropriate integration techniques (such as u-substitution or integration by parts).

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