Lines a and b intersect forming two adjacent angles

Lines a and b intersect forming two adjacent angles
adjacent angle example6
When lines a and b intersect, four angles formed, angle 1, angle 2, angle 3 and angle 4
For angle 1, its adjacent angles are angle 2 and angle 3
Lines a and b intersect forming two adjacent angles
Therefore, when two lines intersect, the sum of its a pair of adjacent angles are 180 degrees.
That is, every pair of adjacent angles are supplementary.