4 congruent triangles are joined together to form a quadrilateral. what quadrilateral is formed?

The quadrilateral that is formed when four congruent triangles are joined together is a square. Here's the step-by-step explanation:

1. First, understand that congruent triangles are triangles that have the same size and shape. This means that all their sides and angles are equal.

2. If you join two congruent triangles at their base, you form a parallelogram. This is because the base angles of the triangles are equal, making the opposite sides of the parallelogram parallel and equal in length.

3. If you join four congruent triangles, you essentially form two parallelograms. But since all the triangles are congruent, all sides of the resulting quadrilateral are equal in length.

4. A quadrilateral with all sides equal in length and all angles equal (since all the base angles of the triangles are equal) is a square.

So, the quadrilateral formed by joining four congruent triangles is a square.