Step-by-step explanation:
You can make use of the properties of parallel lines to prove ∠ACB≅∠DAC.
Statement . . . . Reason
2. ∠DAB +∠ABC = 180° . . . . definition of a right angle
3. AD║BC . . . . consecutive interior angles are supplementary
4. ∠ACB≅∠DAC . . . . alternate interior angles are congruent