And it's a center, a focal point for economic and social development.

So, if this point right here is the point, and we already showed that, this is the point the center of the ellipse is the point 1, minus 2.

This one's fun.

So there's one point that just by looking at it we could say is going to be in our locus.

I'll explain that in just a minute.

Focal length

Focal

Focal Length

Focal blur

Focal point

First Focus

Second Focus

Focal Length

Focal length

And this is f2.

And it's for focus.

Focal length of the lens

Well, we just used the distance formula.

Or they can be, I don't want to say always.

We have focused on the worst case scenario.

That's our directrix and it has the equation y is equal to k.

And what we want to do is, we want to find out the coordinates of the focal points.

Ellipse by Focuses Point

That's what mass marketing is.

35mm equivalent focal length

That's this distance right there.

And that's what we set out to figure out in the beginning.

And you enter that space, and you feel like, Wow!

Requires great focus.

Just focus.

Bifocals.

Your focus,

Hyperbola by Focuses Point

You can't really see it in this map, but this is the map that becomes the central focus in the second half of my book.

Point A is not on the circle, point A is the center of the circle.

I'll call that well, we'll call that a focus because it will be a focus.

But where's the focus point?

So you know that a is equal to x1.

So let's solve for the focal length.

Lieutenant Jiao.

Now, let's see if we can use that to apply it to some some real problems where they might ask you, hey, find the focal length.

Focal Length

Telescope focal length

Eyepiece focal length

So let's call that a directrix.