Download Math 8 Lesson Plan 69D Triangle Inequality Theorem class outline

Sewanhaka High School
Math 8
Class:______________
Mrs. Lidowsky, Principal
Mr. Long, Teacher
Date:________________________
Name:__________________
H.W. #69D: Ditto
DO-NOW #69D: Answer the following questions:
1) In isosceles triangle ABC, the measure of vertex angle C is 30˚ less than the measure of each base angle. Find the number
of degrees in each angle of the triangle. Draw a diagram to help you find your answer.
C
x - 30
x
A
x
B
3) What type of triangle is triangle QRS and why?
Topic: Geometry
Main Idea: Triangle Inequality Theorem
Aim:
RECALL
NOTES
Try to find which set of measurements are the
dimensions of a triangle by developing, on a
separate sheet of looseleaf paper, 4 different
triangles based on their measurements. One of
them will turn out to be a triangle. Your job is to
find which one it is.
(1) 2 in, 3 in, 5 in (2) 4 in, 4 in, 8 in
(3) 3 in, 4 in, 8 in (4) 5 in, 6 in, 7 in
Statement: An easier way of obtaining your
answer is the Triangle Inequality Theorem.
For each of the following, which will form
triangles:
(a) 2,2,3
(b) 6, 8, 10
(c) 6, 8, 20
(d) 4, 4, 12
(e) 5, 5, 10
(f) 6, 4, 4
(g) 15, 12, 9
For each of the above, which of the triangles are
isosceles? Explain.
It states that the sum of the measures of any two sides of any
triangle is greater than the measure of the third side.
Two sides of a triangle have lengths 2 and 5.
Find all possible lengths of the third side.
Drill:
Answer the following:
State if the three numbers can be the measures of the sides of a triangle.
1) 7, 5, 4
2) 3, 6, 2
3) 5, 2, 4
4) 8, 2, 8
5) 9, 6, 5
6) 5, 8, 4
7) 4, 7, 8
8) 11, 12, 9
9) 3, 10, 8
10) 1, 13, 13
11) 2, 15, 16
12) 10, 18, 10
Two sides of a triangle have the following measures. Find the range of possible measures for the
third
side.
13) 9, 5
14) 5, 8
15) 6, 10
16) 6, 9
17) 11, 8
Summary:
If time:
1) Can the given lengths be the measure of a triangle?
a) 5, 3, 7
b) 9, 4, 5
18) 14, 11