Angle 1 is 60 degrees because it is a vertical angle to angle EDF. This means that they are congruent angles formed by two intersecting lines. In other words, angle 1 and angle EDF share the same measurement of 60 degrees. make this shorter and write it in a 7th grade way

Angle 1 and angle EDF are both 60 degrees because they are opposite each other when two lines intersect. This makes them equal in size.