Transcript 11/30 Bell Ringer

In your NOTEBOOK!!!
Write the following two puzzles, and try to
solve them quietly:
Example: He’s/Himself = “He’s beside
himself”
1. ANGLE
ANGLE
ANGLE
2. LAWMOTHERLAW
Lesson 4.1 – Triangle Sum
Today’s Goal
• Formally define a triangle and begin
finding missing angles!
• WHY?
– Triangles are the only rigid polygon
New Material – VOCAB SECTION
∆ABC
Triangle
B
A closed figure
(polygon) with
three sides.
A
Triangle Sum
Theorem
C
The sum of the
1 + 2 + 3 = 180
interior angles of
2
a triangle is equal
3
to 180°
1
In your Notes
• How to find the missing angle
– Step 1: Add two given angles.
– Step 2: Subtract sum from 180.
– Step 3: This is the missing angle.
y
S1: 60 + 70 = 130
S2: 180 – 130 = 50
70°
60°
S3: y = 50°
In your Notes…
• Copy down the following drawings and
identify why it is NOT A TRIANGLE…
WARNING: There may not be a problem!
i.e. It might be a triangle!
1.
2.
50°
75°
Not a closed figure!
No problems!
55°
3.
4.
30°
50°
Angles don’t add to 180
Has 4 sides, not 3
6.
5.
33°
97°
30°
20°
87°
60°
Angles don’t add to 180
No Problem!
Problem of the Day
• What is the value of z in the picture
below?
A. 32°
B. 58°
C. 122°
D. 180°
Homework
Lesson 4.1/ 1 – 9
Vocabulary