CBSE Class 9 Maths Lines and Angles
Basic Concepts of Geometry
A line extends indefinitely in both the directions.
Ray has a fixed starting point but no ending point.Line segment has two end points.
According to Linear Pair axiom: If a ray stands on a line then the sum of the two angles formed is 180 degree. If two lines intersect each other then the vertically opposite angles formed are equal.Parallel Lines and Transversals
Transversal is a line which intersects a pair of lines.
If two parallel lines are intersected by a transversal, then the corresponding angles formed are equal and vice versa.
If two parallel lines are intersected by a transversal, then the alternate interior angles formed are equal and vice versa.Parallel Lines and Co-Interior Angles
If two parallel lines are intersected by a transversal, then the interior angles on the same sides of the transversal are supplementary, and if the co-interior angles are supplementary then the lines are parallel.
If two lines are parallel to the same line then they are parallel to each other.