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PPT: Lines & Angles

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 Page 1


LINES AND LINES AND
ANGLES ANGLES
Page 2


LINES AND LINES AND
ANGLES ANGLES
Point: A Point is that which has no component. It is
represented by a dot.
B A S I C T E R M S
Line: When we join two distinct points then we get a
line. A line has no endpoints it can be extended
infinitely.
Line Segment: It is the part of the line which has two
endpoints.
Page 3


LINES AND LINES AND
ANGLES ANGLES
Point: A Point is that which has no component. It is
represented by a dot.
B A S I C T E R M S
Line: When we join two distinct points then we get a
line. A line has no endpoints it can be extended
infinitely.
Line Segment: It is the part of the line which has two
endpoints.
Ray: Ray is also a part of the line which has only one
endpoint and has no end on the other side.
B A S I C T E R M S
Collinear and Non-collinear points: Points lie on the
same line are known as collinear points and the points
that don't lie on the same line are known as Non-
Collinear Points.
Page 4


LINES AND LINES AND
ANGLES ANGLES
Point: A Point is that which has no component. It is
represented by a dot.
B A S I C T E R M S
Line: When we join two distinct points then we get a
line. A line has no endpoints it can be extended
infinitely.
Line Segment: It is the part of the line which has two
endpoints.
Ray: Ray is also a part of the line which has only one
endpoint and has no end on the other side.
B A S I C T E R M S
Collinear and Non-collinear points: Points lie on the
same line are known as collinear points and the points
that don't lie on the same line are known as Non-
Collinear Points.
B A S I C T E R M S
Page 5


LINES AND LINES AND
ANGLES ANGLES
Point: A Point is that which has no component. It is
represented by a dot.
B A S I C T E R M S
Line: When we join two distinct points then we get a
line. A line has no endpoints it can be extended
infinitely.
Line Segment: It is the part of the line which has two
endpoints.
Ray: Ray is also a part of the line which has only one
endpoint and has no end on the other side.
B A S I C T E R M S
Collinear and Non-collinear points: Points lie on the
same line are known as collinear points and the points
that don't lie on the same line are known as Non-
Collinear Points.
B A S I C T E R M S
W H A T A R E A N G L E S ?
When two rays begin from the
same endpoint then they form
an Angle. The two rays are the
arms of the angle and the
endpoint is the vertex of the
angle.
Angles are measured in degrees.
straight line
straight line
vertex
degrees
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FAQs on PPT: Lines & Angles

1. What's the difference between a line, a line segment, and a ray in geometry?
Ans. A line extends infinitely in both directions with no endpoints, a line segment has two fixed endpoints, and a ray starts at one point and extends infinitely in one direction. Understanding these distinctions is crucial for CBSE Class 9 mathematics, as they form the foundation for studying angles and geometric properties.
2. How do I identify vertically opposite angles and why are they always equal?
Ans. Vertically opposite angles form when two straight lines intersect, creating two pairs of non-adjacent angles across the intersection point. These angles are always equal because they're formed by the same pair of lines; this property holds true regardless of the angle's measurement and is essential for solving geometry problems efficiently.
3. What are corresponding angles and alternate angles when two parallel lines are cut by a transversal?
Ans. When a transversal intersects two parallel lines, corresponding angles are in matching positions on the same side (always equal), while alternate angles lie on opposite sides between the parallel lines (also equal). These angle relationships are fundamental theorems in CBSE geometry and directly help determine whether two lines are parallel.
4. Why do angles on a straight line always add up to 180 degrees?
Ans. Angles on a straight line sum to 180° because a straight line represents a complete, flat surface with no bend-mathematically, this is the definition of a straight angle. This linear pair property is applied constantly in Class 9 geometry to find unknown angles and solve complex angle problems involving intersecting lines.
5. How can I quickly spot complementary and supplementary angles in exam questions?
Ans. Complementary angles sum to 90°, while supplementary angles total 180°. In exams, look for right-angle indicators (small squares) for complementary pairs, and straight-line configurations for supplementary pairs. Practising with flashcards and mind maps on angle relationships helps students recognize these patterns instantly during timed assessments.
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