Let's continue with the angle vocabulary, shall we?

We have two lines that intersect one another. To make things a bit easier for our lesson, the angles are numbered 1, 2, 3, and 4.

vertical angles: two lines that intersect where opposite angles are congruent

What would be the relationship between angles 1 & 2?

They are supplementary or their measures add up to …

What would be the relationship between angles 1 & 4?

They are also supplementary!

Hmm…

So, what do you think the measures of angles 2 & 3 would be?

congruent angles: angles that share the same exact measurement. Keep in mind that the length of the 'legs' do not have to be congruent!

the symbol indicating congruence

adjacent angles: angles that share a common ray/side

Based on the vertical angle definition above, what can you deduce about the following?

Hooray! You have 'graduated' from middle school 'angles' and are now an expert!