Originally Posted by

**magentarita** The **Statement vs. Reason **chart normally used for proofs in high schools across the USA is a common thing.

**COROLLARY**:

**"An exterior angle of a triangle is greater than either remote interior angle." **

Can I prove this corollary using numbers instead of the statement vs reasons chart?

Sample:

Let angle A = exterior angle

Let BCD = a triangle

Let angle B = 70 degrees

Let angle C = 10 degrees

Let angle D = 100 degrees

Then angles A and angle D form a linear pair on a straight line.

Then the measure angle A = 180 degrees - the measure of angle D, which is 100 degrees. The number 180 comes from the fact that a straight line measures 180 degrees.

Of course, 180 - 100 = 80.

So, the measure of angle A = 80 degrees, which is indeed **GREATER THAN** than **EITHER **of the two remote interior angles of 10 degrees and 70 degress.

Can this accepted as the prove for the above corollary without using the statement vs reasons chart that often confuses students far and near?

Also, can this method with numbers be used for any geometric proofs situation?