Triangles
ICSE · Class 9 · Mathematics
Quick revision notes for Triangles — ICSE Class 9 Mathematics. Key concepts, formulas, and definitions for last-minute revision.
Key Topics to Revise
Introduction and Basic Properties
- A triangle is a plane figure bounded by three straight line segments
- Every triangle has three vertices, three sides, and three angles
- The sum of all angles in any triangle is always 180°
Relationship Between Sides and Angles
- In a triangle with unequal sides, the greater side has the greater angle opposite to it
- In a triangle with unequal angles, the greater angle has the greater side opposite to it
- If two sides are equal, their opposite angles are also equal (isosceles triangle property)
Median and Altitude
- A median joins a vertex to the midpoint of the opposite side
- Every triangle has three medians that intersect at the centroid
- The centroid divides each median in the ratio 2:1
Congruent Triangles
- Two triangles are congruent if they have the same shape and size
- Congruent triangles can be superimposed exactly on each other
- Corresponding parts of congruent triangles are equal (CPCTC)
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What are the important topics in Triangles for ICSE Class 9 Mathematics?
Triangles covers several key topics that are frequently asked in ICSE Class 9 board exams. Focus on the core concepts listed on this page and practise related questions to build confidence.
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Start by understanding all key concepts. Practise previous year questions from this chapter. Revise formulas and definitions regularly. Use flashcards for quick revision before the exam.
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