From the figure
angle 1 = angle 2
Angle 1 is alternate to angle 3
Alternate angles are equal
Therefore, angle 1 = angle 3
Angle 2 is alternate to angle 4
Alternate angles are equal
Therefore, angle 2 = angle 4
Angle 1 = Angle 3
Angle 2 = Angle 4
Since Angle 1 = Angle 2
Hence, Angle 3 = Angle 4
