Теория:

Straight lines:
Lenku_veidi_1taisne.png
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.
Example:
45.svg

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:
Lenku_veidi_2taisnes.png
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.
Lenku_veidi_taisne_perp.png
It has written down ab.
Two straight lines, perpendicular to the third, do not intersect.
Lenku_veidi_2taisnes_perp.png