Answer:
The square is the quadrilateral.
Step-by-step explanation:
A quadrilateral is a 2 dimensional geometric shape. It has four sides which may be or may not be equal.
If a quadrilateral is a square and we make its diagonal so that we get two triangles.
These two triangles are isosceles triangle as the two sides are equal and the square has four equal sides and the triangles are congruent to each other.
here, the triangles ABC and ADC are congruent and isosceles.
