The figure below shows a quadrilateral abcd with diagonal bd bisecting angle adc.

which equation is true?

angle abd = angle bcd

angle dcb = angle adb

angle abd = angle cbd

angle abd = angle cdb

So based on the given figure above which is quadrilateral ABCD, the equation that is true would be the third option: angle ABD = angle CBD. Based on the SAS Postulate, if two sides and the included angle of a triangle are congruent to the corresponding sides and angle of another triangle , then the triangles are congruent. Hope that this answer helps.