Download What is the definition of an isosceles triangle?

October 05, 2011
Objective: To apply theorems and corollaries to solve problems
and write proofs about isosceles triangles.
What is the definition of an isosceles triangle?
October 05, 2011
Do you notice anything else?
October 05, 2011
What do you know about
an isosceles triangle now?
Isosceles Triangle Theorem
· If two sides of a triangle are congruent, then
the angles opposite those sides are
_______________.
BAIT (Base Angles Isosceles Triangle)
· If two base angles are congruent, then the
sides opposite those angles are __________.
October 05, 2011
Vertex Angle Bisector (VAB) Cor.
· The bisector of the vertex angle of an
isosceles triangle is
_________________________________.
October 05, 2011
Corollaries
· An equilateral triangle is equiangular.
· An equilateral triangle has three 60
degree angles.
· An equiangular triangle is equilateral.
October 05, 2011
1. Write and test a conjecture about the
lengths of the sides of a triangle.
2. Write and test a conjecture about the
relationship of a triangle's side lengths and
angle measures.
Materials you can use:
· Compass
3 in, 4 in, 5 in
4 cm, 5 cm, 9 cm
Triangle Inequality Theorem
·
The sum of the lengths of any two sides of a triangle is
____________________________ .
Theorem
· In a triangle, the smallest angle is opposite the
____________________ and the largest angle is
opposite the ___________________ .
October 05, 2011
The lengths of two sides of a triangle are 8 and 13. Then,
the length of the third side must be greater than
______ but less than _________ .
Is is possible for a triangle to have sides with lengths
indicated?
a) 6, 8, 10
b) 3, 4, 8
c) 2.4, 4.1, 5