Part A
Angles 1 and 2 (<1 and <2 ) are alternate angles
Alternate angles are angles that are in opposite positions relative to a transversal intersecting two lines
Therefore < 1 and < 2 are equal
Part B
AC and BD are Arc angles
AC = 2 x < 1
BD = 2 x < 2
Since < 1 and < 2 are equal
Then AC = BD
Part C
Parallel lines AB and BC will intercept the AC and BD arcs