The sum of the angles for a 4 sides figure must add up to 360.
Angle 1 and angle 2 are between similar sides so the 2 angles are identical.
Subtract the known angles from 360:
360 - 72 - 18 = 270
Divide that by 2:
270*2 = 135
Angle 2 = 135 degrees.
4.5m questions
5.8m answers