Download Lesson Plan Format

HW: pgs. 336-337 (4-9, 12-14, 34, 35)
5.1, 5.3-5.5 Quiz THURSDAY 12-22
www.westex.org HS, Teacher Website
12-19-11
Warm up—Geometry CPA
B
In the figure to the right,
AB = BC and DE = EF = DF.
If the measure of ABC is 30°
E
and the measure of BDE is 50°,
D
what is the measure of DFA?
A
F
C
Note: Figure not drawn to scale
GOAL:
I will be able to:
1. apply inequalities in one triangle.
HW: pgs. 336-337 (4-9, 12-14, 34, 35)
5.1, 5.3-5.5 Quiz THURSDAY 12-22
www.westex.org
HS, Teacher Website
Name _________________________
Geometry CPA
5-5 Inequalities in One Triangle
Date ________
The positions of the ______________ and _______________ sides of a triangle are
related to the positions of the largest and smallest angles.
Example 1: Ordering Triangle Side Lengths and Angle Measures
a. Write the angles in order
b. Write the sides in order from
from smallest to largest.
shortest to longest.
YOU TRY:
a. Write the angles in order
From smallest to largest.
b. Write the sides in order from
Shortest to longest.
A triangle is formed by three segments, but _______________________ of three segments
can form a triangle.
A certain relationship must exist among the lengths of three segments in order for them to
form a triangle.
http://www.mathopenref.com/triangleinequality.html
Example 2: Applying the Triangle Inequality Theorem
Tell whether a triangle can have sides with the given lengths. Explain.
a. 7, 10, 19
b. 2.3, 3.1, 4.6
c. n + 6, n2 – 1, 3n, when n = 4.
YOU TRY:
a. 8, 13, 21
b. 6.2, 7, 9
c. t – 2, 4t, t2 + 1, when t = 4
Example 3: Finding Side Lengths
The lengths of two sides of a triangle are 8 inches and 13 inches. Find the range of
possible lengths for the third side.
YOU TRY:
The lengths of two sides of a triangle are 22 inches and 17 inches. Find the range of
possible lengths for the third side.
5-5 Practice
1. Write the angles in order
from smallest to largest.
2. Write the sides in order
from shortest to longest.
3. The lengths of two sides of a triangle are 17 cm and 12 cm. Find the range of
possible lengths for the third side.
4. Tell whether a triangle can have sides with lengths 2.7, 3.5, and 9.8. Explain.
5. Ray wants to place a chair so it is 10 ft from his television set. Can the other two
distances shown be 8 ft and 6 ft? Explain.