With reference to the figure, ABCD is a parallelogram. AE and CF are angle bisectors of ∠DAC and ∠ACB respectively. What can you say about lines AE and CF?
Always Parallel
In a parallelogram, opposite angles are equal which means, ∠A = ∠C.
Then, 12 × ∠DAC = 12 × ∠ACB
Thus, ∠EAC = ∠ACF, which are alternate interior angles.
Hence, AE and CF are parallel lines.