Transcript 3-3 Parallel Lines and the Triangle Sum Theorem
L.E.Q. How do you find measures of interior and exterior angles of triangles?
Draw and cut out a large triangle.
Number the angles and tear them off.
Place the three angles adjacent to each other to form one angle.
What do you see?
65º Focus – Prove the Triangle Sum Theorem 25º
The sum of the measures of the angles of a triangle is 180.
m
A
m
B
m
C
180
43
Find the missing angle.
47º
Find the values of x, y, and z.
G 39 21 F x - 11 x J y z H
All 3 angles are congruent.
Has one right angle.
T S U L B S
First tell me this, what is an acute angle?
An acute triangle has three acute angles.
50° 72° 58° 50° 46° 84°
What’s an obtuse angle?
An obtuse triangle has one obtuse angle.
135° W X A 98° M V S
A triangle with no congruent sides.
X 11” 28” W V 20” Can we use tick/dash marks to denote congruence of sides in triangle XWV?
An equilateral triangle has three congruent sides.
3’ 3’ 3’
Has at least two congruent sides.
M J A E F O
An angle that is formed outside the polygon by extending a side of the polygon past its vertex.
The 2 interior angles of a triangle that are nonadjacent to the exterior angle.
The measure of each exterior angle of a triangle is equal to the sum of the 2 remote interior angles.
Add These!
Get This!
T 35 120 U 120º L
Pg 134 – 135 #s 1-15, 24-28 all.