Question

If two lines are parallel than pair of corresponding angles are equal . How ?

Answer 1

because when both line are parralel then measure of angle of corresonding angles becomes 90° which is a straight line or side

Answer 2

Suppose you have two parallel lines cut by a transversal.
Due to the straight angle (linear pair) theorem, we know that
(angle2+angle3=180˚),(angle5+angle6=180˚)
Thought the transitive property, we can say that
angle2+angle3=angle5+angle6 (1)
Though the alternate interior angles theorem, we know that
angle3=angle5
Use substitution in (1):
angle2+angle3 = angle3+angle6
Subtract angle3 from both sides of the equation
angle2=angle6
therefore angle2 congruent angle6
Thus angle2 and angle6 are corresponding angles and have proven to be congruent.