Class 9 Maths — Chapter 6: LINES AND ANGLES
Chapter 6: LINES AND ANGLES is a chapter in Class 9 Maths (NCERT), part of the CBSE NCERT curriculum followed by over 25 million students across India. This chapter covers 8 topics including Basic Geometric Terms, Classification of Angles, Pairs of Angles: Complementary and Supplementary. BrainWeave provides free AI-powered explanations — by voice or text, in Hindi or English — with no signup required.
What you'll learn
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▸Basic Geometric Termslinerayline segmentcollinear pointsnon-collinear
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▸Classification of Anglesacute angleright angleobtuse anglestraight anglereflex angle
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▸Pairs of Angles: Complementary and SupplementaryCore conceptcomplementary anglessupplementary anglessum of angles90 degrees180 degrees
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▸Adjacent AnglesCore conceptadjacent anglescommon vertexcommon armnon-common arms
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▸Linear Pair of AnglesCore conceptlinear pairstraight lineadjacent anglessum 180°
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▸Vertically Opposite AnglesCore conceptvertically opposite anglesintersecting linesopposite raysvertex
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▸Linear Pair AxiomCore conceptlinear pair axiomaxiom 6.1axiom 6.2ray on a lineforms a line
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▸Vertically Opposite Angles TheoremCore concepttheorem 6.1vertically opposite anglesproofequal anglesintersecting lines
Chapter Summary
Understand the definitions and differences between a line, line segment, ray, and identify collinear and non-collinear points.
Define and identify acute, right, obtuse, straight, and reflex angles based on their measures.
Understand the definitions of complementary angles (sum is 90°) and supplementary angles (sum is 180°) and solve problems involving them.
Identify adjacent angles by their key properties: a common vertex, a common arm, and non-common arms on different sides of the common arm.
Understand that a linear pair consists of two adjacent angles whose non-common arms form a straight line, resulting in a sum of 180°.
Identify the pairs of vertically opposite angles formed when two lines intersect each other.
Apply the two axioms related to linear pairs: 1) If a ray stands on a line, the sum of adjacent angles is 180°. 2) If the sum of two adjacent angles is 180°, their non-common arms form a line.
Understand and apply the theorem stating that if two lines intersect, then the vertically opposite angles are equal.
Practice Questions from this Chapter
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- Show real-world angle examples. Get Solution →
- Explain parallel lines simply. Get Solution →
- Discover lines in building designs. Get Solution →
- According to the text, what is a part of a line with two end points called? Get Solution →
- What is the exact measure of a right angle? Get Solution →
- What is the sum of two complementary angles? Get Solution →
- If three or more points lie on the same line, what are they called? Get Solution →
- An angle that is greater than 180° but less than 360° is called a... Get Solution →
Did you know?
- 💡 The ancient Babylonians likely chose 360 degrees for a circle because it is easily divisible.
- 💡 Bees perform a "waggle dance" using angles to tell other bees where to find food.
- 💡 The Great Pyramid of Giza was built with nearly perfect right angles and straight lines.
- 💡 Although light usually travels in straight lines, massive objects can bend light's path.
- 💡 A straight line is the shortest path between two points only on a flat surface.
Frequently Asked Questions
How many topics are covered in this chapter?
This chapter covers 8 key topics: Basic Geometric Terms, Classification of Angles, Pairs of Angles: Complementary and Supplementary, Adjacent Angles, Linear Pair of Angles, and more. The BrainWeave AI tutor explains each one with examples.
Is Chapter 6: LINES AND ANGLES important for board exams?
Class 9 is a foundation year. Mastering this chapter now will help you build strong fundamentals for the higher classes.
Can I get NCERT solutions for this chapter in Hindi?
Yes. BrainWeave's AI tutor supports Hindi, English, and Hinglish for both voice and text chat. Just ask your question in your preferred language.
Is BrainWeave free for Class 9?
Yes. BrainWeave's free Spark plan gives generous daily messages — enough for regular homework. Premium features unlock when you bring your own free Google Gemini API key.
Can I use voice chat for this chapter?
Absolutely. Tap the mic, ask any question about Chapter 6: LINES AND ANGLES, and the AI tutor will explain it back in voice and text.
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