Theorem 6.1 :-
If two lines intersect each other, then the vertically opposite angles are equal.
Given :- Two lines AB and CD intersecting at point O.
To Prove :- Vertically opposite angles are equal
i.e, AOC = BOD
and AOD= BOC
Proof :-
From (1) and (2)
AOC + BOC = AOD + AOC
BOC = AOD
Now,
To prove BOD = AOC
From (3) and (4)
AOD + BOD = AOD + AOC
BOD = AOC
Hence, Vertically Opposite angles are equal.

Made by

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths and Science at Teachoo.