20 Must-Know Geometry Theorems for SSC CGL & CHSL

Geometry carries 6-8 questions in SSC CGL. Knowing these 20 theorems will cover 90% of all geometry questions asked in SSC exams.

Triangle Theorems

1. Angle sum property: All angles = 180°. 2. Exterior angle theorem: Exterior angle = sum of non-adjacent interior angles. 3. Midpoint theorem: Line joining midpoints of two sides is parallel to third side and half its length.

Circle Theorems

4. Angle in semicircle = 90°. 5. Equal chords subtend equal angles at center. 6. Tangent-radius perpendicularity. 7. Angle at center = 2 × angle at circumference.

Quadrilateral Properties

8. Parallelogram: Diagonals bisect each other. 9. Rectangle: Diagonals are equal. 10. Rhombus: Diagonals are perpendicular bisectors.

Quick Tip

For SSC, draw diagrams for every geometry question. Mark given information clearly. The answer often becomes obvious from the diagram itself.