Keaton wrote the following paragraph proof for the Vertical Angles Theorem: The sum of angle 1 and angle 4 and the sum of angle 3 and angle 4 are each equal to 180 degrees _______________. The sum of angle 1 and angle 4 is equal to the sum of angle 3 and angle 4 by the transitive property of equality. Angle 1 is equal to angle 3 by the subtraction property of equality. Which phrase completes the proof?
For the Vertical Angle theorem, if a slant line is intersected by a horizontal, the opposite angles must be equal. In here, he stated that the sum of angle 1 and angle 4 and the sum of angle 3 and angle 4 are each equal to 180 degrees. It means that the sum of angle 1 and angle 4 is equal to the sum of angle 3 and angle 4 by the transitive property of equality.
