Maths · KS3 Y9 · Geometry & Measures

Geometric reasoning chains

Geometric reasoning chainsFree12:56Heddy Score 3 of 7, below the standard

What you need to know

  • The angles inside any triangle add up to 180°, so a missing angle is 180° minus the other two.
  • An equilateral triangle has three equal sides and three 60° angles.
  • An isosceles triangle has two equal sides, and the angles opposite them are equal.
  • Triangles can also be named by their angles: acute, right-angled or obtuse.

In this clip

0:00–2:11Special triangles
Also coversGeometric reasoning chains
Heddy Score3/7, Below the standard
See the seven stars
  • Trusted source · passed. The creator's own upload, live and playable here.
  • On the map · not judged yet. A teacher watched it: it mainly teaches this map topic.
  • Spec-true · not judged yet. Accurate, and right for the current UK specification.
  • Focused · passed. One idea, short enough to watch in one go.
  • Accessible · passed. Good captions, clear sound and pictures.
  • Safe for children · not judged yet. Right for 11 to 16 year olds, with no sales pitch.
  • Proven · not judged yet. Earned from our students: they learn from it, find it helpful and watch it to the end.
★ passed · ☆ pending · ✕ failed
Our students

Not enough students yet

Our own students' answers. These are what move ★7 Proven.
On YouTube

588K views · 19K likes · Brain Station 584K subscribers

As reported by YouTube on 2026-11-02. Not part of the Heddy Score.
How the Heddy Score works

Why we picked it

A brisk opening that names the special triangles and links each one to what its angles must be.

Brain Station on YouTubechecked 2026-10-22

Plays from youtube-nocookie.com. No YouTube cookies until you press play.