1.3 Measuring Angles Lesson Essential Question: How do you accurately measure angles and use the Angle Addition Postulate? Bellringer 1. ) Which "Building Block of Geometry" term would accurately describe the two hands on a clock? a) line segment b) angle c) ray d) point 2.) The distance from town A to town C is 50 miles. Town B is in between towns A and C. The distance from town A to town B is 22 miles. What is the distance from town B to town C? a) 72 miles b) 30 miles c) 28 miles d) 38 miles
Four Types of Angles Right AngleDefinition Example Acute Angle Obtuse Angle Straight Angle
What are the steps to measuring an angle? 1. Use a protractor (which is used to measure angles). 2. Put the center of the protractor at the vertex. (where the two rays meet) 3. Align the protractor so that the bottom ray passes through 0 on the protractor. 4. Read the measure of the angle (using the appropriate scale) at the point where the other ray intersects the protractor.
Construct the following angles · Remember the directions on how to construct angles using a protractor m ABC = m DEF = m YXZ = m MNP = 180
Congruent Angles Which an gles are ≅ ? Ang le Congruence Postulate (1.3.2) If two (2) angles have the same measure, then they are congruent. If two (2) angles are congruent, then they have the same measure. A C B D
Bellringer Write an example of a acute, obtuse, right, and straight angle
Angle Addition Postulate (1.3.3) If point S is in the interior of PQR then m PQS + m SQR = m PQR VISUAL EXAMPLE Inde pendent Practice B E M T If m BTM = 39, m BTE = (3x - 6), and m ETM = (x + 25), then find the following... 1.) What is the value of x? ______________________ 2.) What is the m BTE? _______________________
Special Angle Pairs (1.3.4) Complimentary angles are 2 angles whose measures have a sum of 90. Each angle is called the complement of the other. Example Supplementary angles are 2 angles whose measures have a sum of 180. Each angle is called the supplement of the other. Example
If the endpoint of a ray falls on a line so that 2 angles are formed, then the angles are known as a linear pair. 1 and 2 form a linear pair. Linear Pair Property (1.3.5) If 2 angles form a linear pair, then they are supplementary. EXAMPLE 1 2 (2x + 24) (6x - 2)