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Geometry · SS1

Angles, triangles & polygons

Angle facts on lines and in triangles and polygons: the reasons every geometry answer quotes.

Leads to
Construction & lociCircle geometryPlane mensurationTrigonometric ratios

Learn

  1. 1Angles and parallel linesAngles on a straight line and at a point, vertically opposite angles, corresponding, alternate and co-interior angles, and the extra parallel line that solves a bend between two parallels.Done15 min
  2. 2Angles in trianglesThe angle sum of a triangle, the exterior angle rule, isosceles and equilateral triangles, and chains of isosceles triangles.Done15 min
  3. 3Polygons and quadrilateralsThe interior angle sum (n − 2) × 180°, exterior angles adding to 360°, regular polygons and finding the number of sides, and the properties of the special quadrilaterals.Done16 min
  4. 4Pythagoras, congruent and similar trianglesPythagoras' theorem and the common triples, the four tests for congruent triangles, and similar triangles: matching the sides, a line parallel to one side, and areas scaling by k².Done16 min

Practise

Answer angles, triangles & polygons questions one at a time. You'll know straight away whether you're right, with hints and the working step by step.

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Past questions (151)

From 1983–2025: 72 WAEC, 9 NECO, 70 JAMB. Theory questions first, then objective, newest first.

Theory (40)

Objective (111)