Angles on lines, in triangles, in polygons

Angles on a straight line add to 180 degrees, angles round a point add to 360, and the angles of a triangle add to 180. Almost every angle chase is those three facts applied in turn until the unknown is cornered.

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LearnWhat it is, how to spot it, a worked example, and where it goes wrong.
Practice — 3-point ladder5 problems. Three in a row finishes it.0/3 in a row · 0/5 solved
Practice — 4-point ladder2 problems. Three in a row finishes it.0/3 in a row · 0/2 solved
Practice — 5-point ladder1 problem. Three in a row finishes it.0/3 in a row · 0/1 solved
Skill quizFinish every ladder that has problems first.Finish the ladders above first

Before and after

Needs first

Nothing. This is one of the skills the Atlas starts from.

Opens up

GEO-06Properties of triangles and quadrilaterals GEO-18Clock geometry: hands, angles, times

In official papers

No indexed official paper question has been tagged with GEO-05 yet. The index grows one paper at a time, and it records only question numbers, point values and our own skill tags — never the problems themselves.

See the papers indexed so far

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