Video: Identifying the Line of Reflection That a Known Triangle Is Reflected on to Gain Another Known Triangle

Video Transcript

In which line must triangle 𝐹𝐷𝐿 be reflected to map it onto triangle 𝐹𝐶𝐿?

Let’s start by highlighting triangle 𝐹𝐷𝐿 and triangle 𝐹𝐶𝐿. Here’s triangle 𝐹𝐷𝐿. And here’s triangle 𝐹𝐶𝐿. In a reflection, every point is the same distance from the central line. And the central line is the line that is being reflected over.

Our points 𝐹 and 𝐿 are not changing. Point 𝐷 turns into point 𝐶. Point 𝐷 and point 𝐶 are the same distance from the line 𝐹𝐸. 𝐶 is four units away from the line 𝐹𝐸. And 𝐷 is four units away from the line 𝐹𝐸. Because points 𝐹 and 𝐿 lie on the central line, they won’t change.

Triangle 𝐹𝐷𝐿 can be reflected over line 𝐹𝐸 to produce triangle 𝐹𝐶𝐿.