# Function inner product

## Main Question or Discussion Point

Dear all:
I have a problem about the inner product of a function. Give a function

$$\begin{displaymath} f(x) = \left\{ \begin{array}{ll} x & \textrm{if x \in [0,1]}\\ -x+2 & \textrm{if x \in (1, 2]} \end{array} \end{displaymath} \{$$

What's the value of the inner product of the function itself over [0,2]?
$$\begin{displaymath} <f(x), f(x)> = \int_{x=0}^{x=2} f(x)f(x) d_x \end{displaymath}$$]

If given another function
$$g(x) = \left\{ \begin{array}{ll} x-1 & \textrm{if x \in [1,2]}\\ -x+3 & \textrm{if x \in (2, 3]} \end{array} \{$$

What's the inner product of f(x) and g(x) please?

Last edited:

For you first question you have to seperate integral into two
One of them is from 0 to 1, the other is from 1 to 2.

For the second you have to explain on which interval we take the inner product they are from different worlds.

I know the principle actually. Could you give me the whole details please? Because I can't get the correct answer.

For question1
You have to get from integral(0-1) =1/2 and from integral(1-2) =1/3
If you did not then write what you did .Maybe we can find the mistake
It would be yours or mine

Last edited:
for question 2 : I am still waiting an explanation
It can be only defined on [1,2] i think

Last edited:
It's possible that the intention is that f and g vanish wherever not explicitly defined. Then you would be right, it would be like on [1,2]...