1. Angle Addition Postulate Classify angles
1.4 Angles and Measures
Angle Addition Postulate
Classify angles

2. Definition of an angle
Two rays that have the same initial point called the Vertex Named ∠ABC A All angles are named with three letters. B The middle letter is the vertex. C

3. Angle Measure
We use a protractor to measure angles and is given a letter m before the name when standing for its measure. m∠ABC = 50ᵒ, so the angle has a measurement of 50 degrees.

4. The Protractor Postulate like the Ruler postulate for angles
The measure of an angle is the absolute value of the different of the terminal side and the initial side. X
terminal side
50 ᵒ Y
Initial side Z

5. Angles can be also be Congruent
Again the definition of Congruent is Same Shape and Same Size. If m∠XYZ = m∠ABC, then ∠XYZ≌∠ABC. If ∠PQR≌∠FMB, then ∠PQR≌∠BMF, but not ∠PQR≄∠MBF. Order is important! The vertex must be in the middle

6. Angles have an Interior and an Exterior
K Q Interior Exterior X

7. The Angle Addition Postulate
If P is in the interior of ∠RST, then m∠RSP + m∠PST = m∠RST T m∠TSP = 12ᵒ P m∠PSR = 24ᵒ S R m∠RST = 36ᵒ

8. Classifying Angles
Acute Right Obtuse 0 to less then 90ᵒ degrees More then 90ᵒ degrees 90ᵒ degrees Straight Angle equals 180ᵒ

9. Adjacent Angles
Adjacent means next to each other; the same as adjacent lockers. Adjacent lockers share one wall. Adjacent angles share one side and have a common vertex. ∠ABC and ∠CBX are A C adjacent angles B X

10. Homework
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