Two Angles are Supplementary when they add up to 180 degrees. They don't have to be next to each other, just so long as the total is 180 degrees. Examples: 60° and 120° are supplementary angles.
Angles 2, 3 and 4 are taking up 180 degrees because it is 1/2 of a circle. That means angles 1 and 5 are also taking up 180 degrees because both the angles add up to a straight line
