Work in groups to answer the questions. Try your best.
1. Name 2 pair of alternate interior angles5 & 3 and 4 & 1
2. What is the sum of m1 + m2 + m3? 180°
3. If m4 = 65° and m5 = 50°, what is m2?
65°
1 32
4 5
4. Find all the angle measures50°
40°
90°
40° 40°
90° 130°
50°
50°
Vocabulary
• Adjacent angles – angles that share a common vertex and side
• Vertical angles – a pair of non-overlapping angles that are opposite and congruent to each other when two lines intersect
• Complementary angles – two angles whose sum of angle measures equals 90 degrees
• Supplementary angles – two angles whose sum of angle measures equals 180 degrees
• Congruent angles – angles whose angle measurements are equal
continued . . .• Axes – the vertical and horizontal lines that act as a
reference when plotting points on a coordinate plane• Exterior angles of a triangle – angles that are outside
of a triangle between one side of a triangle and the extension of the adjacent side
• Interior angles of a triangle – angles that are inside of a triangle, formed by two sides of the triangle
• Transversal – a line that intersects two or more lines• Angle-angle criterion for triangles – if two angles in
one triangle are congruent to two angles in another triangle, then the measure of the third angle in both triangles are congruent
Objectives---What we’ll learn…
• Find the measurement of a missing angle by using Triangle Angle Sum Theorem.
• Find the measurement of a missing angle by using Exterior Angle Theorem.
Isosceles Triangles & Angle Sum Theorem
E + W + H = 180o
W H
E + 2(W) = 180o
Base Angles are congruent.
Exterior Angle Theorem
The measure of an exterior angle in a triangle is the sum of the measures of the 2 remote interior angles
exterior angle
remote interior
angles
A = C + D
Exterior Angle Theorem
The measure of an exterior angle in a triangle is the sum of the measures of the 2 remote interior angles
3
2
1 4
exterior angle
remote interior
angles
4 = 1 + 2
Shortcut:
Interior 1 + Interior 2 + Interior 3 = 1800
= 1800
1. Triangle INTERIOR Angle Sum
2. Triangle EXTERIOR Angle Sum
Remote Interior 1
+ Remote Interior 2 = Exterior Angle
= Exterior Angle