MathematicsClass 6Basic Geometrical Ideas
Triangles and Quadrilaterals
Studying three-sided and four-sided polygons and their basic structural properties.
Class 6 · MathematicsCBSE & ICSE
Definition
A triangle is a simple closed curve made of three line segments, possessing three sides and three angles. A quadrilateral is a four-sided polygon bounded by four line segments, having four vertices and four angles.
Key formula
Sum of interior angles of a triangle = 180 degrees
Worked examples
1
A triangular road sign or a slice of pizza represents a triangle.
2
A chessboard square, a blackboard surface, and a windowpane represent quadrilaterals.
3
A truss bridge structure made entirely of connected triangles for stability.
Common mistakes
- • Thinking that a triangle can have four sides if it looks deformed.
- • Forgetting that quadrilaterals include shapes other than squares and rectangles, such as trapeziums and parallelograms.