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CBSE 9th Math CH 10 - Lines and Angle Notes and Solutions | Pratap Sanjay Sir

CBSE 9th Math CH 10 - Lines and Angle Notes and Solutions | Pratap Sanjay Sir

Angle

An angle is formed by two rays or two line segments that have a common endpoint called the vertex.

Interior Angle

An interior angle is an angle formed inside a polygon by two adjacent sides.

Exterior Angle

An exterior angle of a polygon is an angle formed outside the polygon by extending one of its sides.

Congruent Angles

Congruent angles are angles that have the same measure.

Angle Measure Axiom

The angle measure axiom states that the measure of an angle is a unique number between 0 and 360 degrees.

Types of Angles

  1. Right Angle
  2. Acute Angle
  3. Obtuse Angle
  4. Straight Angle
  5. Reflex Angle
  6. Complementary Angles
  7. Supplementary Angles
  8. Angle Bisector
  9. Adjacent Angles
  10. Linear Pair of Angles
  11. Vertically Opposite Angles
  12. Transversal
  13. Corresponding Angles
  14. Alternate Interior Angles
  15. Consecutive Interior Angles

Right Angle

An angle that measures exactly 90 degrees.

Example: The angle formed between the hour and minute hand at 3 o'clock.

Acute Angle

An angle that measures less than 90 degrees.

Example: The angle formed by two hands of a clock at 1 o'clock.

Obtuse Angle

An angle that measures more than 90 degrees but less than 180 degrees.

Example: The angle formed by two hands of a clock at 10 o'clock.

Straight Angle

An angle that measures exactly 180 degrees.

Example: The angle formed by a straight line on a sheet of paper.

Reflex Angle

An angle that measures more than 180 degrees but less than 360 degrees.

Example: The angle formed by the minute hand of a clock at 10 o'clock.

Complementary Angles

Two angles whose sum is 90 degrees.

Example: An angle of 30 degrees and an angle of 60 degrees are complementary.

Supplementary Angles

Two angles whose sum is 180 degrees.

Example: An angle of 120 degrees and an angle of 60 degrees are supplementary.

Angle Bisector

A line or ray that divides an angle into two equal parts.

Example: The bisector of a 90-degree angle divides it into two 45-degree angles.

Adjacent Angles

Two angles that share a common vertex and a common side but do not overlap.

Example: In a rectangle, adjacent angles are formed at each vertex.

Linear Pair of Angles

Two adjacent angles that form a straight line, totaling 180 degrees.

Example: Angles at the ends of a straight line, such as angles in a straight angle.

Vertically Opposite Angles

Angles that are opposite each other when two lines intersect; they are equal in measure.

Example: The angles formed by the intersection of two straight lines.

Transversal

A line that intersects two or more other lines at distinct points.

Example: A line intersecting two parallel lines forms corresponding angles.

Corresponding Angles

Angles that occupy the same relative position at each intersection where a straight line crosses two others.

Example: Angles formed when a transversal crosses two parallel lines.

Alternate Interior Angles

Angles that are on opposite sides of the transversal and inside the two lines, but on different lines.

Example: Angles formed on the inside of two lines when a transversal crosses them.

Consecutive Interior Angles

Angles that are on the same side of the transversal and inside the two lines, but on different lines.

Example: Angles formed on the inside of two lines when a transversal crosses them.

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