So in this case I've got an input that looks like this.

I've got a high frequency superimposed on a low frequency, so

I can actually kind of see what the two parts to it too are.

That's the low frequency component in the red dashed, and

then the high frequency is super imposed on it.

So I've got two frequencies going in, and

the output of this circuit gives something like this.

So in the frequency domain, I've got two frequencies,

a low frequency which is this one in red, and then the high frequency.

The low frequency is at 50 radians per second,

high frequency at 800, both have an amplitude equal to 1.

Now I put it through this transfer function and

at 50, the value is, say, about 0.9,

and at 800 the value is about 0.2.