Transcript S D Inv. 2.4 B-D Ins and Outs of Polygons.pptx

Math CC7/8 – Be Prepared
On Desk:
1. Pencil
2. Math Journal
3. Learning Log
Learning Log:
• HW: WS –Angle
Sums & Ext. Angles
• Quiz – Tue. 9/15
Fundraiser – Keep selling!
Curriculum Night – Tomorrow 6-8 PM
Tasks for Today
•
•
•
•
HW Questions/Issues?
S & D inv. 2.4 B-D
Learning Check Inv. 2
Begin HW?
p. 50
Sum of the interior angles is:
S = (n -2) 180
S = (5 – 2) 180
or S = 3(180)
Sum of the exterior angles is 360 , but we can view that as
2(180)
So… total sum of interior and exterior angles (T) is:
T = 3(180) + 2(180)
or T = (3+2)180
T = 180(5)
T = 180n – 360 is the total interior angle measure.
The 360 can be thought of as 180(2).
T = 180n – 180(2)
Using the Distributive Property, we can now see that
we have the formula developed in lesson 2.2, which is
T = (n-2)180
3(180)
360
3(180) – 360 = 180
Total – exterior = interior
x + 2x + 3x = 180
6x = 180
x = 30, 2x = 60, 3x = 90
Supplements:
x + 2x + x – 20 = 180
4x - 20 = 180
4x = 200
X = 50, 2x = 100, x – 20 = 30
Supplements: