1. Lines
Section 5.1
Essential question: How are the measures of angles related when parallel lines are cut by a transversal?
t/parallelandperpendicularlines/

2. Vocabulary
When two lines intersect in a plane and form right angles they are called __________________________. Two lines are called _________________ when they are in the same plane and do not intersect.

3. Graphic Organizer Parallel Lines Perpendicular Lines Symbols
Define it in your own words
Draw it
Describe a real-world example of it

4. Key Concept: Transversals and Angles
A line that intersects two or more lines is called a _______________, and eight angles are formed
______________ lie inside the lines.
Examples: ___________________
______________ lie outside the lines.

5. Key Concept: Transversals and Angles
__________________ are interior angles that lie on opposite sides of the transversal. When the lines are parallel, their measures are equal. Examples: ________________
__________________ are exterior angles that
lie on opposite sides of the transversal. When the
lines are parallel, their measures are equal.
Examples: ____________________

6. Key Concept: Transversals and Angles
___________________ are those angles that are in
the same position on the two lines in
relation to the transversal. When the lines
are parallel, their measures are equal.
Examples: ______________________

7. Examples
Classify each pair of angles in the figure as alternate interior, alternate exterior, or corresponding.
1. ∠4 and ∠8
2. ∠1 and ∠7
3. ∠2 and ∠6

8. Notes: Find Missing Angle Measures
When two parallel lines are cut by a transversal, special angle relationships exist.
If you know the measure of one of the angles, you can find the measures of all of the angles.
Suppose you know that the measure of angle 1 is equal to 50 degrees. You can use that to find the measures of angles 2, 3, and 4.
m ∠ 2 =
Because ______________________________
m ∠ 3 =
m ∠ 4 =
Because _______________________________

9. Examples
If m∠4 = 122°, find each given angle measure. Justify your answer.
1. m∠8
2. m∠5
3. m∠2
4. m∠1

10. Essential Question
How are the measures of the angles related when parallel lines are cut by a transversal?
______________________________________________________________________________