How do you prove that 2 angles are equal in a parallelogram?

1 Answer
Mar 1, 2018

See below


In a parallelogram , the opposite angles are equal.


So as you can see parallelogram has opposite sides parallel. So adjacent angles must sum up to 180°(because if the angle is more or less the lines would converge on either side)

Let ABCD be ||gm (||gm means parallelogram, it is a short notation)
#angleA+angle B=180°#

#angle B+angle C=180°#

Using elimination, substitution or whatever

#angleA-angle C=0°#

#angle A=angle C#
Hence proved