They lie outside the two lines on opposite sides of the transversal.
They are congruent in the case of two parallel lines cut by a transversal.
Now, let's draw two horizontal lines cut by a transversal. Notice that all horizontal lines are parallel to each other. Let x^(∘) represent one of the angle measures.
Now, let's find angles that form corresponding, vertical, or alternate exterior angles with our angle. They will also have a measure of x^(∘).
Next, notice that each of the remaining angles is a supplementary angle to one of the angles with the measure of x^(∘). This means that the rest of angles have the measure of 180^(∘)-x^(∘).
We have found the measure of every angle. Therefore, the least number of angle measures we need to know to find measure of every angle for the given situation is 1.
