What do you use as reason to support the step of a geometric proof?

In a geometric proof, reasons to support each step can include definitions, postulates, theorems, and previously proven statements. For example, one might use the definition of congruent triangles to justify that two triangles are congruent, or apply the Pythagorean theorem to establish a relationship between the sides of a right triangle. Logical reasoning and established properties of geometric figures also serve as essential support for each step in the proof.