📘 Chapter 6: Triangles – Class 10 Maths Notes

📘 Chapter 6: Triangles – Class 10 Maths Notes

🔺 Introduction

Triangles are 3-sided polygons. In this chapter, you’ll learn about similar triangles and important theorems.

📐 1. Similar Figures

Similar figures have the same shape but not necessarily the same size.
Examples: All circles, all equilateral triangles.

🔻 2. Similar Triangles

Triangles with equal angles and proportional sides are similar.

📏 3. Criteria for Similarity

• AA Criterion: Two equal angles → triangles are similar
• SSS Criterion: All sides in same ratio → similar
• SAS Criterion: Two sides in ratio + included angle equal → similar

🔣 4. Basic Proportionality Theorem

If DE || BC in triangle ABC, then AD/DB = AE/EC

🧮 5. Area of Similar Triangles

Area₁ / Area₂ = (Side₁ / Side₂)²

📐 6. Pythagoras Theorem

In a right triangle:
Hyp² = Base² + Height²

🧠 Key Points

• AA, SSS, SAS → Triangle similarity
• Thales’ theorem divides sides proportionally
• Pythagoras theorem for right triangles

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