the vertex are written as same sa angles eg 

angle a is equal to angle b

vertex a is equal to vertex b

so no need to write both no .we can write only one

Dear Student!

 Vertex and angles are although related but still not the same thing. Vertex is a point, while angle is formed by the intersection of two lines, which meet at a vertex. Moreover there is a possibility of more than one angle at a single vertex, so it may create confusion. So, you should not use vertex in place of angles.

Got it!