Okay, so I haven't done proofs in a bit, so when it comes to proving that lines are congruent (or angles), you can try to prove that the triangles are congruent (CPCTC- Corresponding Parts of Congruent Triangles are Congruent). To prove that triangles are congruent, use SSS (Side side side- meaning all sides are congruent), ASA (angle side angle- meaning corresponding angle, then side, then angle are congruent), SSA (2 corresponding sides are congruent and an angle is also congruent) or SAS (you get it). We should use ASA, since obviously it says that ABD and CBD are congruent and obviously BD and BD are congruent and ADB aND CDB are congruent (both are 90degrees). So, we have proven that these traingles are congruent. Now use CPCTC as the last step, since AD and CD are corresponding parts of the triangles.
