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NCERT · Ganita Prakash · Volume 1 · Chapter 5

Parallel and Intersecting Lines

58 videos in this chapter

Angles at an intersection

2 videos

Chapter 5Why Do Adjacent Angles on a Line Add to 180°?3:04Why Do Adjacent Angles on a Line Add to 180°?You'll learn: Adjacent angles that form a straight line together make 180°.Chapter 5Why Are Vertically Opposite Angles Equal?3:10Why Are Vertically Opposite Angles Equal?You'll learn: A single equality proof needs the linear-pair deductions to remain visible.

Geometric facts versus measurements

1 video

Chapter 5Why Does Measuring a Diagram Not Prove a Geometric Fact?3:38Why Does Measuring a Diagram Not Prove a Geometric Fact?You'll learn: Measuring a drawing can suggest a fact, but drawings are imperfect, so a proof is needed.

Perpendicular lines

1 video

Chapter 5Why Do Four Equal Intersection Angles Make Perpendicular Lines?3:22Why Do Four Equal Intersection Angles Make Perpendicular Lines?You'll learn: If four angles at an intersection are equal, each is 90°, so the lines are perpendicular.

Parallel lines and segment intersections

2 videos

Chapter 5When Do Segments Meet—and What Happens If We Extend Them?3:22When Do Segments Meet—and What Happens If We Extend Them?You'll learn: Segments can meet at endpoints, midpoints or interior points, and extending them can create new meeting points.Chapter 5Why Must Parallel Lines Lie in the Same Plane?3:15Why Must Parallel Lines Lie in the Same Plane?You'll learn: Lines that never meet but lie in different planes are not parallel; parallel lines must share a plane.

Lines through paper folding

2 videos

Chapter 5Make Parallel and Perpendicular Creases by Folding3:27Make Parallel and Perpendicular Creases by FoldingYou'll learn: Fold paper to make parallel and perpendicular creases and spot the repeating pattern.Chapter 5Read Parallel-Line Arrows and Right-Angle Squares3:37Read Parallel-Line Arrows and Right-Angle SquaresYou'll learn: Arrows mark parallel lines and a small square marks a right angle in diagrams.

Transversals and distinct angle measures

1 video

Chapter 5Why Do Eight Transversal Angles Have at Most Four Measures?3:27Why Do Eight Transversal Angles Have at Most Four Measures?You'll learn: A transversal makes eight angles from two vertically opposite pairs at each crossing, so at most four different measures.

Corresponding angles and parallelism

2 videos

Chapter 5Find Corresponding Angles on Parallel Lines3:32Find Corresponding Angles on Parallel LinesYou'll learn: When lines are parallel, angles in matching positions at the two crossings are equal.Chapter 5Use Corresponding Angles to Test Whether Lines Are Parallel3:26Use Corresponding Angles to Test Whether Lines Are ParallelYou'll learn: If corresponding angles are equal the lines are parallel; if they differ, the lines meet somewhere.

Drawing parallel lines

2 videos

Chapter 5Draw a Parallel Line with a Ruler and Set Square3:21Draw a Parallel Line with a Ruler and Set SquareYou'll learn: Slide a set square along a ruler to draw a line parallel to a given line.Chapter 5Create Parallel Lines by Paper Folding3:24Create Parallel Lines by Paper FoldingYou'll learn: Fold paper twice at right angles to create parallel lines.

Alternate and same-side interior angles

4 videos

Chapter 5Why Are Alternate Interior Angles Equal on Parallel Lines?3:13Why Are Alternate Interior Angles Equal on Parallel Lines?You'll learn: Alternate interior angles are equal because each equals the same corresponding angle.Chapter 5Why Do Same-Side Interior Angles Add to 180°?3:21Why Do Same-Side Interior Angles Add to 180°?You'll learn: One same-side interior angle equals the angle forming a linear pair with the other, so the two add to 180°.Chapter 5Find Missing Angles in a Parallel-Line Diagram

Parallel illusions

1 video

Chapter 5Are These Lines Really Parallel—or Is It an Illusion?3:22Are These Lines Really Parallel—or Is It an Illusion?You'll learn: Optical illusions can make parallel lines look bent; check with measurements and angle facts.

Parallel and Intersecting Lines

40 videos

Chapter 5Will These Lines Meet If We Extend Them?3:36Will These Lines Meet If We Extend Them?You'll learn: Will These Lines Meet If We Extend Them?Chapter 5Four Angles at an Intersection: Measure and Look for Patterns3:38Four Angles at an Intersection: Measure and Look for PatternsYou'll learn: Four Angles at an Intersection: Measure and Look for Patterns Chapter 5Linear Pairs: Why Adjacent Angles Add to 180 Degrees3:29

3:08

Find Missing Angles in a Parallel-Line Diagram

You'll learn: Chain corresponding, alternate and linear-pair facts to find missing angles.

Chapter 5Draw an Extra Parallel Line to Unlock an Angle Problem3:08Draw an Extra Parallel Line to Unlock an Angle ProblemYou'll learn: Drawing an extra parallel line through a corner turns a hard angle problem into known angle pairs.

Linear Pairs: Why Adjacent Angles Add to 180 Degrees

You'll learn: Linear Pairs: Why Adjacent Angles Add to 180 Degrees

Chapter 5Why Vertically Opposite Angles Are Equal3:25Why Vertically Opposite Angles Are EqualYou'll learn: Why Vertically Opposite Angles Are Equal

Chapter 5Why Measurements May Differ from Geometric Predictions3:44Why Measurements May Differ from Geometric PredictionsYou'll learn: Why Measurements May Differ from Geometric Predictions

Chapter 5Four Equal Angles: Recognising Perpendicular Lines3:26Four Equal Angles: Recognising Perpendicular LinesYou'll learn: Four Equal Angles: Recognising Perpendicular Lines

Chapter 5Describing How Line Segments Meet3:43Describing How Line Segments MeetYou'll learn: Describing How Line Segments Meet

Chapter 5What Makes Two Lines Parallel?3:36What Makes Two Lines Parallel?You'll learn: What Makes Two Lines Parallel?

Chapter 5Finding Sets of Parallel Lines in a Drawing3:28Finding Sets of Parallel Lines in a DrawingYou'll learn: Finding Sets of Parallel Lines in a Drawing

Chapter 5Repeated Paper Folds: Parallel Creases and a Counting Pattern3:38Repeated Paper Folds: Parallel Creases and a Counting PatternYou'll learn: Repeated Paper Folds: Parallel Creases and a Counting Pattern

Chapter 5Making Parallel Diagonal Folds and Folded Triangles3:39Making Parallel Diagonal Folds and Folded TrianglesYou'll learn: Making Parallel Diagonal Folds and Folded Triangles

Chapter 5Marking Parallel and Perpendicular Lines Correctly3:43Marking Parallel and Perpendicular Lines CorrectlyYou'll learn: Marking Parallel and Perpendicular Lines Correctly

Chapter 5Drawing Perpendicular Lines on Dot Paper3:29Drawing Perpendicular Lines on Dot PaperYou'll learn: Drawing Perpendicular Lines on Dot Paper

Chapter 5Drawing Parallel Lines on Dot Paper3:31Drawing Parallel Lines on Dot PaperYou'll learn: Drawing Parallel Lines on Dot Paper

Chapter 5Which Slanted Line Is Really Parallel?3:32Which Slanted Line Is Really Parallel?You'll learn: Which Slanted Line Is Really Parallel?

Chapter 5A Transversal Makes Eight Angles: How Many Can Be Different?3:34A Transversal Makes Eight Angles: How Many Can Be Different?You'll learn: A Transversal Makes Eight Angles: How Many Can Be Different?

Chapter 5Finding All Four Pairs of Corresponding Angles3:39Finding All Four Pairs of Corresponding AnglesYou'll learn: Finding All Four Pairs of Corresponding Angles

Chapter 5Copying an Angle to Create Parallel Lines3:29Copying an Angle to Create Parallel LinesYou'll learn: Copying an Angle to Create Parallel Lines

Chapter 5Why Parallel Lines Have Equal Corresponding Angles3:32Why Parallel Lines Have Equal Corresponding AnglesYou'll learn: Why Parallel Lines Have Equal Corresponding Angles

Chapter 5Can Nonparallel Lines Have Equal Corresponding Angles?3:50Can Nonparallel Lines Have Equal Corresponding Angles?You'll learn: Can Nonparallel Lines Have Equal Corresponding Angles?

Chapter 5Drawing Parallel Lines with a Ruler and Set Square3:29Drawing Parallel Lines with a Ruler and Set SquareYou'll learn: Drawing Parallel Lines with a Ruler and Set Square

Chapter 5Using the Long Edge of a Set Square to Draw Parallels3:30Using the Long Edge of a Set Square to Draw ParallelsYou'll learn: Using the Long Edge of a Set Square to Draw Parallels

Chapter 5Drawing a Parallel Through a Given Point3:32Drawing a Parallel Through a Given PointYou'll learn: Drawing a Parallel Through a Given Point

Chapter 5Making a Parallel Through a Point by Paper Folding3:17Making a Parallel Through a Point by Paper FoldingYou'll learn: Making a Parallel Through a Point by Paper Folding

Chapter 5Finding Alternate Angles Across a Transversal3:28Finding Alternate Angles Across a TransversalYou'll learn: Finding Alternate Angles Across a Transversal

Chapter 5Proving Equal Alternate Angles on Parallel Lines3:28Proving Equal Alternate Angles on Parallel LinesYou'll learn: Proving Equal Alternate Angles on Parallel Lines

Chapter 5Finding All Eight Angles When One Angle Is 135 Degrees3:26Finding All Eight Angles When One Angle Is 135 DegreesYou'll learn: Finding All Eight Angles When One Angle Is 135 Degrees

Chapter 5Using Unequal Corresponding Angles to Reject Parallelism3:32Using Unequal Corresponding Angles to Reject ParallelismYou'll learn: Using Unequal Corresponding Angles to Reject Parallelism

Chapter 5Why Same-Side Interior Angles Add to 180 Degrees3:21Why Same-Side Interior Angles Add to 180 DegreesYou'll learn: Why Same-Side Interior Angles Add to 180 Degrees

Chapter 5Following Angle Relationships in a Shape with Two Parallel Pairs3:07Following Angle Relationships in a Shape with Two Parallel PairsYou'll learn: Following Angle Relationships in a Shape with Two Parallel Pairs

Chapter 5Angle Practice: Straight Lines and Crossing Lines3:34Angle Practice: Straight Lines and Crossing LinesYou'll learn: Angle Practice: Straight Lines and Crossing Lines

Chapter 5Angle Practice: Connected Crossings and Parallel Lines3:26Angle Practice: Connected Crossings and Parallel LinesYou'll learn: Angle Practice: Connected Crossings and Parallel Lines

Chapter 5Angle Practice: Combining Several Angles Around a Point3:34Angle Practice: Combining Several Angles Around a PointYou'll learn: Angle Practice: Combining Several Angles Around a Point

Chapter 5Finding the Unknown Angle in Four New Configurations3:40Finding the Unknown Angle in Four New ConfigurationsYou'll learn: Finding the Unknown Angle in Four New Configurations

Chapter 5Finding X and Y from Parallel-Line Angle Relationships3:39Finding X and Y from Parallel-Line Angle RelationshipsYou'll learn: Finding X and Y from Parallel-Line Angle Relationships

Chapter 5Transferring Angles Through a Network of Lines3:12Transferring Angles Through a Network of LinesYou'll learn: Transferring Angles Through a Network of Lines

Chapter 5Three Parallel Lines and a Perpendicular: Find Both Angles3:30Three Parallel Lines and a Perpendicular: Find Both AnglesYou'll learn: Three Parallel Lines and a Perpendicular: Find Both Angles

Chapter 5Solving a Bent-Line Angle Problem by Adding Parallels3:24Solving a Bent-Line Angle Problem by Adding ParallelsYou'll learn: Solving a Bent-Line Angle Problem by Adding Parallels

Chapter 5Are Those Lines Really Parallel? Exploring Visual Illusions3:44Are Those Lines Really Parallel? Exploring Visual IllusionsYou'll learn: Are Those Lines Really Parallel? Exploring Visual Illusions

Chapter 5Parallel and Intersecting Lines: Chapter Recap3:47Parallel and Intersecting Lines: Chapter RecapYou'll learn: Parallel and Intersecting Lines: Chapter Recap