Answer:
As ∠1 and ∠4 makes straight line t so their sum should be equal to 180°
∠1 + ∠4 = 180° (makes pair of supplementary angles)------------------------(1)
Similarly ∠3 and ∠4 makes straight line AB so their sum should also be equal to 180°
∠3 + ∠4 = 180° (makes pair of supplementary angles)------------------------(2)
From equations (1) and (2) we get
∠1 + ∠4 = ∠3 + ∠4 (as both were equal to 180°)
subtracting ∠4 from both sides we get
∠1 + ∠4 - ∠4 = ∠3 + ∠4 -∠4
∠1 = ∠3
Hence, proved that verticaly opposite angles ∠1 and ∠3 are equal
