Draw the diagram and mark the sides that are congruent as well as the angles.
△ ABD ≅ △ CBD
Practice makes perfect
To prove △ ABD ≅ △ CBD, we have to show that two sides and the included angle of one triangle are congruent to the corresponding sides and the included angle of the other.
A square has four right angles and four congruent sides. Let's incorporate this information in our diagram.
Let's remove the unnecessary angles from the diagram.
Knowing that one of the angles and the two sides that form that angle in one triangle are congruent with the corresponding parts in the other triangle, we can use the SAS Congruence Theorem to write a congruence statement.
△ ABD ≅ △ CBD.
