GEO005 · Geometry basics · Classes 7–9
Parallel lines and transversal
A transversal crosses two parallel lines. Corresponding angles are equal, alternate angles are equal, and co-interior angles add to 180°.
∥ + transversalParallel lines and transversal
📐 Formula
corresponding = alternate = θ; co-interior = 180° − θ
✏️ Worked example
θ = 65°: corresponding 65°, alternate 65°, co-interior 115°.
🌍 Where it is used
Railway tracks, ladders, road markings and window frames.
❓ Quick check
Co-interior angles between parallel lines add to…
🏋️ Practice
EasyOne corresponding angle is 70°. The other?
Answer: 70°
MediumAlternate angle to 48°?
Answer: 48°
ChallengeCo-interior angle to 110°?
Answer: 70°