U-Substitution

Topic Notes

You may start to notice that some integrals cannot be integrated by normal means. Therefore, we introduce a method called U-Substitution. This method involves substituting ugly functions as the letter "u", and therefore making our integrands easier to integrate. We will use this technique to integrate many different functions such as polynomial functions, irrational functions, trigonometric functions, exponential functions and logarithmic functions. We will also integrate functions with a combination of different types of functions.

Pre-requisite:
* Differential Calculus –"Chain Rule"
* Integral Calculus –"Antiderivatives"
Note:
The main challenge in using the

u-Substitution

is to think of an appropriate substitution.
- Question: how to choose

u

?
- Answer: choose

u

to be some function in the integrand whose differential also occurs!

hint:

u

is usually the inside of a function, for example:

- the inside a power function:

( u )^{10}

- the inside a radical function:

\sqrt{u}

- the inside of an exponential function:

e^u

- the inside of a logarithmic function:

\ln

(u)

- the inside of a trigonometric function:

\sin

(u)