Class 11 Mathematics — Chapter 9: STRAIGHT LINES

What you'll learn

• ▸Recap of Coordinate Geometry Formulae
• ▸Slope and Inclination of a Line
• ▸Calculating Slope from Two Points
• ▸Conditions for Parallelism and Perpendicularity
• ▸Angle Between Two Lines
• ▸Collinearity of Three Points

Chapter Summary

--- PAGE 1 --- Chapter 9 STRAIGHT LINES ⁂ Geometry, as a logical system, is a means and even the most powerful means to make children feel the strength of the human spirit that is of their own spirit. – H. FREUDENTHAL ⁂ 9.1 Introduction We are familiar with two-dimensional coordinate geometry from earlier classes. Mainly, it is a combination of algebra and geometry. A systematic study of geometry by the use of algebra was first carried out by celebrated French philosopher and mathematician René Descartes, in his book 'La Géométrie, published in 1637. This book introduced the notion of the equation of a curve and related analytical methods into the study of geometry. The resulting combination of analysis and geometry is referred now as analytical geometry. In the earlier classes, we initiated the study of coordinate geometry, where we studied about coordinate axes, coordinate plane, plotting of points in a plane, distance between two points, section formulae, etc. All these concepts …

Practice Questions from this Chapter

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1. Connect lines to building architecture. Get Solution →
2. Illustrate coordinate systems in everyday objects. Get Solution →
3. Explain why Descartes is important. Get Solution →
4. Who is credited with the systematic study of geometry by the use of algebra in his book 'La Géométrie'? Get Solution →
5. What is the formula for the distance between two points P(x₁, y₁) and Q(x₂, y₂)? Get Solution →
6. If θ is the inclination of a line l, what is the definition of the slope (m) of the line? Get Solution →
7. What is the condition for two non-vertical lines with slopes m₁ and m₂ to be parallel? Get Solution →
8. What is the inclination of a line that is parallel to the x-axis? Get Solution →

Did you know?

• 💡 Coordinate geometry helps describe shapes using only numbers.
• 💡 Ancient Egyptians used straight lines to re-survey land after Nile floods.
• 💡 A laser beam is one of the best real-world examples of a straight line.
• 💡 The shortest distance between any two points in space is always a straight line.
• 💡 René Descartes reportedly invented coordinates while watching a fly on his ceiling.

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