1. Lines and Angles Intro

2. Classify angles by size Classify angles by size
Quick Review:
Classify angles by size
Classify angles by size
Acute: 0<90
Right: 90
Obtuse: 90<180
Straight: 180

3. Intersecting Lines: Perpendicular Lines: Parallel Lines:
Lines in a plane that intersect (or cross)
Can cross at any angle
Examples:
Perpendicular Lines:
Lines that intersect at a right angle (90°)
Symbol for perpendicular
Symbol for not perpendicular
Parallel Lines:
Lines in a plane that do not intersect (will never cross)
Symbol for parallel lines is II
Symbol for not parallel lines is II

4. Adjacent Angles: Vertical Angles: Linear Pair:
Have a shared vertex and shared side
(they are ‘next to’ each other or ‘touching’)
Examples:
Vertical Angles:
Formed by intersecting lines, but are non-adjacent
(they are ‘across the vertex’ from each other, don’t share a side)
Vertical Angles are congruent (equal angle measure)
Linear Pair:
2 adjacent angles that form a straight line
(they make a straight line together)
Straight Line = 180° = a linear pair

5. Supplementary Angles:
Two angles whose sum is 180°
Two angles who together form a straight angle/straight line
(because a straight line is 180°)
Examples:
Complementary Angles:
Two angles whose sum is 90°
Two angles who together form a right angle
(because a right angle is 90°) J K
130°
50°
<J & <K are supplementary. 1 2
<1 and <2 are supplementary M J K O
<JKO & <MKO are complimentary A B
40°
50°
<A & <B are complementary.

6. *Tip: How to remember which is which? Think:
"C" of Complementary stands for "Corner" 
Corner is a Right Angle
"S" of Supplementary stands for "Straight"
180 degrees is a straight line

7. Find the Missing Angle Find the measure of <1 1 Solution:
63°
Solution:
Since <1 and the 63° angle are a linear pair (form a straight line together), they must add to 180°.
If <1 is unknown, call it x.
Write an equation to find the unknown angle.
x + 63 = 180
x = 117
<1 = 117° x
63°

8. Find the Missing Angle Angle x and angle y are supplementary angles.
If angle y is 3 times greater than the measure of x, what is the measure of each angle? x y
Solution:
Since <x and <y are supplementary, they must add to 180°.
If <x is unknown, call it x.
If <y is three times <x, then <y must be = 3x because it will be 3 times bigger.
*tip- express all unknowns in terms of just one variable (not two)
Write an equation to find the unknown angle.
x + 3x = 180
4x = 180
x = 45
<x = 45° and <y = 135° x 3x