What part of a triangle changes when the third vertex is moved?

When the third vertex of a triangle is moved, it causes the lengths of the triangle's sides to change, which in turn affects the perimeter. The perimeter of a triangle is calculated by adding the lengths of all three sides. As the position of the third vertex is altered, the lengths of the sides corresponding to that vertex will also change, resulting in a different perimeter for the triangle.

The angles of the triangle, while they can also be influenced by moving a vertex, can remain the same depending on how the vertex is moved. The base and height may also be affected by the movement, but they do not encapsulate the overall change in the triangle’s structure in terms of total length. The perimeter specifically refers to the total distance around the triangle, making it the most direct aspect impacted when repositioning a vertex.