DO NOW Constructing a Segment Bisector Draw ST on your transparency paper. Fold the paper so point S is lying on point T. In the crease draw a dotted line labeled m.

Homework Questions

How do we name and classify angles?

1-3 Measuring and Constructing Angles An angle is a figure formed by two rays, or sides, with a common endpoint called a vertex. vertex

1-3 Measuring and Constructing Angles The set of all points between the sides of the angle is the interior of an angle. The exterior of an angle is the set of all points outside the angle. S 1 R T Angle Names: S, RST, TSR, 1 *The vertex is always the middle letter*

1-3 Measuring and Constructing Angles S 1 R T *You cannot name an angle just by its vertex if it is the vertex of more than one angle* Q List the names for 1.

1-3 Measuring and Constructing Angles The measure of an angle is given in degrees. 360 Each degree is of a circle

1-3 Measuring and Constructing Angles Protractor Postulate: Given AB and a point O on AB, all rays that can be drawn from O can be put into a one-to-one correspondence with real numbers from 0 to 180. A B O 0°

1-3 Measuring and Constructing Angles Types of Angles 0° Acute Angle M easures greater than 0 and less than 90 Right Angle M easures 90 Obtuse Angle M easures greater than 90 and less than 180 Straight Angle F ormed by two opposite rays and measures 180

1-3 Measuring and Constructing Angles Measuring Angles 0° m ABC = B A C (measure)

1-3 Measuring and Constructing Angles 0° m ABC = m DEF B A C Congruent angles are angles that have the same measure. E D F So, ABC ≅ DEF congruency marks

0° Constructing Congruent Angles C B A D

C B Constructing Angle Bisectors A

1-3 Measuring and Constructing Angles 0° Angle Addition Postulate: If S is in the interior of PQR, then m PQS + m SQR = m PQR Q P R S

1-3 Measuring and Constructing Angles 0° m ABD = 37 and m ABC = 84. Find m DBC B A C D m ABC = m ABD + m DBC 84 = 37 + m DBC m DBC = 47

1-3 Measuring and Constructing Angles 0° KM bisects JKL Angle Bisectors are rays that divide angles into two congruent angles. K J L So, JKM ≅ MKL M

1-3 Measuring and Constructing Angles 0° BD bisects ABC, m ABD = (6x + 3), and m DBC = (8x - 7). Find m ABD. B A C D m ABD = m DBC (6x + 3) = (8x - 7) 3 = 2x = 2x x = 5 m ABD = 6(5) + 3 m ABD = 33

How do we name and classify angles?

Homework: pg. 24 # 1-10, 17, 18, 27 0° What do you call a person who favors tractors? A Protractor!