There are different terms used in geometry. They are:
There are various types of angles. They are:
When the angle is of 90°, it is called right angle
When the angle is less than 90°, it is known as acute angle.
When the angle is greater than 90° but less than 180°, it is called obtuse angle.
When the angle is more than 180° but less than 360°, it is called reflex angle.
When the angle is of 180°, it is called straight angle.
When the angle is of 360°, it is known as complete angle.
When the sum of measures of two angles is 90°, they are said to be complementary angles. Eg., 30° and 60° is a pair of complementary angles.
When the sum of measures of two angles is 180°, they are said to be supplementary angles. Eg., 75° and 105° is a pair of supplementary angles.
Two angles are said to be adjacent if:
- They have same vertex
- They have a common arm
- Uncommon arms are on the either side of the common arm
Vertically Opposite Angles
When two lines intersect, four angles are formed. The angles opposite to each other are called vertically opposite angles.
Two adjacent angles form a linear pair of angles, when their non-common arms are two opposite rays.
If two parallel lines are intersected by a transversal, then
- Each pair of corresponding angles is equal.
- Each pair of alternate angles is equal.
- Interior angles on the same side of the transversal are supplementary.