Class 7 Mathematics — Chapter 7: A Tale of Three Intersecting Lines

What you'll learn

• ▸Basics of a Triangle
• ▸Equilateral and Isosceles Triangles
• ▸Constructing Triangles with SSS Criterion
• ▸The Triangle Inequality Property
• ▸Verifying Triangle Possibility
• ▸Reasoning about Non-Triangles

Chapter Summary

--- PAGE 1 --- 7 A TALE OF THREE INTERSECTING LINES 0774CH07 A triangle is the most basic closed shape. As we know, it consists of: * three corner points, that we call the vertex of the triangle, and * three line segments or the sides of the triangle that join the pairs of vertices. Triangles come in various shapes. Some of them are shown below. A X U B Y Z V W A U C ΔABC ΔYZX ΔWUV ΔBAU Observe the symbol used to denote a triangle and how the triangles are named using their vertices. While naming a triangle, the vertices can come in any order. The three sides meeting at the corners give rise to three angles that we call the angles of the triangle. For example, in ΔABC, these angles are ∠CAB, ∠ABC, ∠BCA, which we simply denote as ∠A, ∠B and ∠C, respectively. ? What happens when the three vertices lie on a straight line? 7.1 Equilateral Triangles Among all the triangles, the equilateral triangles are the most symmetric ones. These are triangles in which all the sides are o…

Practice Questions from this Chapter

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1. Explain how triangles are used in bridges. Get Solution →
2. Show me how to use a compass. Get Solution →
3. Quiz me on types of triangles. Get Solution →
4. What are the three corner points of a triangle called? Get Solution →
5. What is the defining characteristic of an equilateral triangle? Get Solution →
6. Which symbol is commonly used to denote a triangle? Get Solution →
7. According to the text, which tool, besides a ruler, makes constructing an equilateral triangle more efficient? Get Solution →
8. A triangle that has two equal sides is called what? Get Solution →

Did you know?

• 💡 Triangles are the strongest shapes, making them essential in construction and engineering.
• 💡 Ancient Egyptians used geometry, including triangles, to build the Great Pyramids.
• 💡 The oldest known ruler, made of copper, dates back over 5,000 years to ancient Mesopotamia.
• 💡 A 'triangle' is also a musical instrument played by striking a metal bar.
• 💡 All triangles, no matter their shape, have internal angles that always add up to 180 degrees.

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