Name the sides of angle one.
Let’s start by identifying where angle one is on the given figure. This is angle one. We have to name its sides. Let’s start on the vertex 𝑋. And here we can draw the first line, which ends at point 𝑌. So we can call the first side line 𝑋𝑌. Now let’s draw the second line. We’re starting at point 𝑋, the vertex again. And it’s this line here which ends at point 𝑈. And we call this line 𝑋𝑈. The sides of angle one are line 𝑋𝑌 and line 𝑋𝑈.