Question Video: Identifying Angles Mathematics • 4th Grade

Name the angle formed by ray 𝐹𝐶 and ray 𝐹𝐵.


Video Transcript

Name the angle formed by ray 𝐹𝐶 and ray 𝐹𝐵.

In the picture, we can see several rays. We know that a ray starts from an endpoint and then continues in one direction. For example, the ray 𝐹𝐴 starts at this point here, continues through point 𝐴, and this arrowhead on the end shows that we’re talking about a ray because it continues on and on in a single direction.

Now, our question talks about two other rays that we can see in the diagram: ray 𝐹𝐶 and ray 𝐹𝐵. How do we know that these symbols represent rays? Well, if we think about the first one for a moment, we can see two letters. The first letter is our endpoint. The second letter is a point that our ray travels through. And importantly, on top of them, we can see an arrow pointing in one direction.

Let’s try and find this ray on the diagram. It begins at point 𝐹. It travels through point 𝐶 and continues out the other side, on and on and on. So where’s our second ray, ray 𝐹𝐵? Well, once again, we’re starting from the same point, point 𝐹. This time though, we’re going to travel through point 𝐵 on and on beyond point 𝐵. So our question mentions two rays, but did you notice they share an endpoint? And that’s point 𝐹 here. And we know that where two rays meet at a single endpoint, they make an angle.

Now, our question asks us to name this angle. We could look at the vertex and write the symbol for angle and then just the letter 𝐹. And we could say that we’re talking about angle 𝐹. But there are lots of angles in this diagram, and they’ve all got 𝐹 as their vertex. We’re going to have to list all three points, and we’re going to write the vertex in the middle. So if we want to name this angle, we could start by writing the angle sign and then write point 𝐵, then 𝐹, that’s the vertex of our angle, and finally 𝐶. We can represent the angle formed by rays 𝐹𝐶 and 𝐹𝐵 by drawing the angle symbol and then writing the letters 𝐵𝐹𝐶.

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