It's equidistant from a focus and a directrix, where this is the focus.

And this is f2.

And it's for focus.

This doesn't cause any damage.

And you essentially divide 1 by 4 times this value.

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

That's this distance right there.

Same thing, that's this line.

And hard to keep focus.

Show camera aperture and focal length

Ellipse by Focuses Point

Hyperbola by Focuses Point

Let's take it right there.

Focal length

Focal

Focal Length

Focal blur

Focal point

First Focus

Second Focus

Focal Length

Focal length

So let's call that a directrix.

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

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

Well, the first thing you do is though I've never well, we could just figure out the focal length just by plugging into the formula.

The scaling factor was 1.

An ellipse constructed by its focuses and a point that pertains to it

We also know that the projection of the building on the internal chip is 4mm in size.

This is f1, this is f2.

Set here equivalent focal length assuming a 35mm film camera, in mm. A value of 0 means the focal length is unknown.

Let's focus on the conversations between our friends and our family and our coworkers and our loved ones.

We have focused on the worst case scenario.

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

A hyperbola constructed by its focuses and a point that pertains to it

Conic by Directrix, Focus Point

Construct a conic with this point as focus

It looks something like that.

That's the point.

And now we should be able to use this information to figure out the actual coordinates of the focus and the directrix of what I would call the classic parabola, y is equal to x squared.

In this case the major axis is the vertical axis, so the focuses are going to sit here and here, and in this case, the focal lengths are going to be vertical down from the origin and vertical up from the origin, and we get, instead of it being a squared minus b squared, now since b is larger than a, the focal length, which is this, is going to be equal to b squared minus a squared.

So you know that a is equal to x1.

We say we have a parabola, and we're saying that this parabola is the set of all points that's equidistant between some focus and some directrix.

Now we're asking you what is the focal length if an object of size 20 m that is 400 meters out if we observe it to be 1 mm on our projection surface.

The square root of that.