Corresponding Angles Postulate If a transversal intersects 2 || lines, then corresponding s are .

Solve for “x”.

4x = 48 x = 12

Alternate Interior Angles Theorem

Alternate Interior Angles Theorem

Alternate Interior Angles Theorem If a transversal intersects 2 || lines, then alternate interior s are .

In the picture a || b. Solve for x. Find the measure of the two angles.

5x – 54 = 3x + 16 2x = 70 x = 35 Each  is 121o.

Alternate Exterior Angles Theorem

Alternate Exterior Angles Theorem

While it’s good to know the names of the angles, the most important thing is that when lines are parallel, angles that look alike are congruent.

Same-Side Interior Angles Theorem

Same-Side Interior Angles Theorem These angles aren’t .

Same-Side Interior Angles Theorem

Assuming the lines are parallel, solve for “x” and find the measures of the two angles.

3x + 40 + 2x + 60 = 180 5x + 100 = 180 5x = 80 x = 16 3x + 40 88o 2x + 60 92o

Find the measure of every labeled angle in the picture.

a = 70o … Why?

Since a = 70o, e = 70o … Why?

b = 45o … Why?

Since b = 45o, d = 45o … Why?

Since d = 45o and e = 70o, c = 65o … Why?

Since f = 130o … Why?

Assuming the lines are parallel, what information can you determine from this picture?

2, 3, and 6 are all 45o 1, 5, and 8 are all 135o

5x + 35 = 135 … so x = 20

If lines are parallel, corresponding, alternate interior, and alternate exterior angles are all congruent.

If lines are parallel, same-side interior angles are supplementary.