L1 · Sides of polygons: perpendicular, parallel, equal

Learning goal

“I can describe the sides of a polygon: which sides are equal, which sides are parallel (they stay the same distance apart and never meet), and which sides are perpendicular (they meet at a right angle, like a book corner).”

Polygon — a closed shape with straight sides: triangles, quadrilaterals, pentagons, hexagons, and octagons are polygons.

Side — one straight edge of a polygon. A polygon has exactly as many sides as vertices.

Parallel sides — sides that stay the same distance apart and never meet, like the two rails of a train track.

Perpendicular sides — sides that meet at a right angle, like the two edges that form the corner of a book.

Worked example

Picture a rectangle drawn on the board: a long top side, a long bottom side, and two short sides joining them. The top side and the bottom side run in the same direction. They stay the same distance apart along their whole length, and if you extended them forever they would never meet. Sides like that are parallel. The left side and the right side are also parallel to each other. So a rectangle has two pairs of parallel sides. Say it plainly: parallel is not 'both slanted' or 'both straight' - the test is: same distance apart, never meeting.

Check yourself — explain it

Can two sides of a triangle ever be parallel?

Paired problem — example still visible

The cover of a book is a rectangle. Name a pair of parallel sides on the cover -> The top edge and the bottom edge (also: the left edge and the right edge)

Faded completion — last step is yours

"The two rails of a railway track stay the same distance apart and never meet, so the rails are ___ sides." -> parallel

Ready to practise?

10 scored questions with a 3-rung hint ladder. Mastery needs 8/10 plus both gate questions.

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