Straight lines:
The angle AOB=180°  is a wide-angle, and a beam \(OC\) divides it into two parts then 1+2=180°.
The sum of two angles on a straight line is 180°, such angles are called Supplementary angles.
When two angles are supplementary, each angle is said to be the supplement of the other.

AOB  and ∠BOC - adjacent angles

AOB  + ∠BOC  = ∠AOC .

AOC  and ∠COP- linear pair.
Therefore, their sum is 180°  (∠AOC  + ∠COP  = 180°).
Combining these two results we get ∠AOB  + ∠BOC  + ∠COP  = 180°.
Thus, the sum of all the angles formed at a point on a straight line is 180°.
Intersecting lines:
If two lines intersect, then two pairs of vertical angles are formed 1,3 and 2,4.
1+2=180° and 1+4=180°  by the property of adjacent angles, therefore, 2=4.
It is also clear that 1=3.
Vertical angles are equal.
Perpendicular lines and angles formed by them
If one of the vertical angles of the line is equal to 90°, then the remaining angles are also straight.
If two intersecting straight lines form four right angles, they are called perpendicular.
It has written down ab.
Two straight lines, perpendicular to the third, do not intersect.