L1 · Sides of Polygons: Parallel, Equal, Perpendicular

Learning goal

“I can describe the sides of a polygon in words: which sides are parallel, which sides are equal in length, and which sides are perpendicular - using measurements, not just looks.”

Parallel — two sides are parallel when they run in exactly the same direction and never meet, like train tracks. They stay the same distance apart everywhere.

Perpendicular — two sides are perpendicular when they meet at a square corner (a right angle), like the corner of a page.

Equal in length — two sides are equal in length when measuring shows they have exactly the same length - not just when they look the same.

Worked example

One rectangle, measured: top side 6 cm, right side 4 cm, bottom side 6 cm, left side 4 cm. Step 1 (parallel): The top and bottom sides run in the same direction and never meet - they are parallel. The left and right sides are also parallel to each other. Step 2 (equal in length): Top = 6 cm and bottom = 6 cm: equal in length. Left = 4 cm and right = 4 cm: equal in length. Opposite sides of a rectangle are equal. Step 3 (perpendicular): The top side meets the right side at a square corner - they are perpendicular. Every neighbouring pair in a rectangle is perpendicular. Say it plainly: these three words - parallel, equal in length, perpendicular - are how we describe sides with proof. "Looks slanted" is not a description; a measurement is.

Check yourself — explain it

Why do we measure sides instead of just looking at them?

Paired problem — example still visible

A triangle has sides 7 cm, 7 cm, 4 cm. Which sides are equal in length? -> The two 7 cm sides

Faded completion — last step is yours

"Two sides that run the same way and never meet, like train tracks, are called ___ 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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