Parallel lines and a transversal · समांतर रेखाएँ और तिर्यक रेखा
Eight angles, two sizes. Name the pair, then find the missing angle.
Parallel lines and a transversal games
Angles made by a transversal समांतर रेखाएँ और तिर्यक रेखा
A transversal (तिर्यक रेखा) is a line that cuts two lines. When it cuts two parallel lines it makes 8 angles:
| Pair | Angles | Rule (lines parallel) |
|---|---|---|
| Corresponding संगत कोण | 1 & 5, 2 & 6, 3 & 7, 4 & 8 | Equal |
| Alternate interior एकांतर अंतः कोण | 3 & 6, 4 & 5 | Equal |
| Alternate exterior | 1 & 8, 2 & 7 | Equal |
| Co-interior (same side) एक ही ओर के अंतः कोण | 3 & 5, 4 & 6 | Add up to 180° |
| Vertically opposite | 1 & 4, 2 & 3, 5 & 8, 6 & 7 | Equal (always) |
| Linear pair | 1 & 2, 3 & 4, … | Add up to 180° (always) |
Quick trick: in this picture every angle is either the small (acute) one or the big (obtuse) one. Small + big = 180°. Also see angles and angle sum of a triangle.
Goes with NCERT Maths Class 7 (Lines and angles) and Class 9.
A one-page chart to stick on the wall, and a worksheet to practise.
Parallel lines and a transversal
Angles made by a transversal समांतर रेखाएँ और तिर्यक रेखा
A transversal (तिर्यक रेखा) is a line that cuts two lines. When it cuts two parallel lines it makes 8 angles:
| Pair | Angles | Rule (lines parallel) |
|---|---|---|
| Corresponding संगत कोण | 1 & 5, 2 & 6, 3 & 7, 4 & 8 | Equal |
| Alternate interior एकांतर अंतः कोण | 3 & 6, 4 & 5 | Equal |
| Alternate exterior | 1 & 8, 2 & 7 | Equal |
| Co-interior (same side) एक ही ओर के अंतः कोण | 3 & 5, 4 & 6 | Add up to 180° |
| Vertically opposite | 1 & 4, 2 & 3, 5 & 8, 6 & 7 | Equal (always) |
| Linear pair | 1 & 2, 3 & 4, … | Add up to 180° (always) |
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Parallel lines and a transversal — worksheet
Name: ____________________ Class: ______ Date: __________
1. If ∠1 = 120°, find ∠5 = ____ ∠8 = ____ ∠2 = ____
2. If ∠3 = 70°, find ∠6 = ____ ∠5 = ____
3. Name a pair of alternate interior angles: ______
4. Co-interior angles add up to ______
5. Draw two parallel lines and a transversal. Mark a pair of corresponding angles.
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