Maths Chapter 05: Lines and Angles
Class 07 Maths NCERTA line-segment has two end points. A ray has only one end point (its initial point); and a line has no end points on either side.
An angle is formed when two lines (or rays or line-segments) meet.
Two complementary angles: Measures add up to 90°
Two supplementary angles: Measures add up to 180°
Two adjacent angles have a common vertex and a common arm but no common interior.
When two lines l and m meet, we say they intersect; the meeting point is called the point of intersection.
When lines drawn on a sheet of paper do not meet, however far produced, we call them to be parallel lines.
When two lines intersect (looking like the letter X) we have two pairs of opposite angles. They are called vertically opposite angles. They are equal in measure.
A transversal is a line that intersects two or more lines at distinct points. A transversal gives rise to several types of angles.
When a transversal cuts two parallel lines,
- Each pair of corresponding angles are equal.
- Each pair of alternate interior angles are equal.
- Each pair of interior angles on the same side of transversal are supplementary.