Question

how to prove intersecting lines are equal

Answer 1

draw 2 intersecting lines ab and cd and mark all the angles 1 2 3 and 4 the write this as the proof
Given two lines AB and CD intersect each other at the point O.
To prove: ∠1 = ∠3 and ∠2 = ∠4
Proof:
From the figure, ∠1 + ∠2 = 180°  [Linear pair]  → (1)
∠2 + ∠3 = 180°  [Linear pair]  → (2)
From (1) and (2), we get
∠1 + ∠2 = ∠2 + ∠3
∴ ∠1 = ∠3
Similarly, we can prove ∠2 = ∠4 also.