And I'll talk about more types of angles in the next video, but if an angle is less than 90 degrees so for example both of these angles that we started our discussion with are less than 90 degrees we call them acute angles.

This angle plus this angle is going to be equal to this angle.

Let's say it a little generally.

An angle of 90 degrees is called a right angle.

Some people would call this the reflexive property

Even if your paper doesn't have an edge, you can just fold it and ta da Angle A Tron!

This length is equal to this length.

This is a right angle and then, this is a right angle

Now, we can use that exact same logic

This is a right angle

And this measure of how fast you're orbiting around a central point is called angular velocity

So angle angle side orange sorry, orange angle white angle side

So we know that this is a right angle

Now the other thing that we know

And on top of that, what makes is even more extreme, is the actual angle that the... and of course this is to some degree due the fact of where the angle of the Sun in relative to the horizon or where you are on Earth, but even more than that, if you are on...

Now, both of these triangles are also isosceles triangles, so their base angles are going to be the same. So that's one base angle, that's the other base angle.

Now what else can we figure out?

This is a 90 degree angle here.

Arc angle

Shadow Angle

Degrees

Radius

Angle

Angle

X angle

Y angle

Angle

X angle

Y angle

Do I do it upside down?

And if you look at it that way you'll immediately see that angle

Obviously, this is a right angle

All right, choice A. 55.

So we could draw that here.

That means that that this angle here must be equal to 90 degrees minus alpha, which means this angle, since this is a right triangle must be alpha.

And that's the best angle of the courtyard?

And they want to know, what is a measure in degrees of the

So, for example, we know that angle CDE is going to be congruent to angle BAE

Well, you might realize that we've just shown that both of these triangles, they have this pink angle and they have this side in common and then they have the green angle

Trigonometric functions use degree mode for angles.

But this is just general terminology for different types of angles

Angle value in degrees.

Angular velocity

Seed radius

Cut off angle