Download Theorem 4.6 Isosceles Triangle Theorem (ITT)

Geometry Section 4.6 NMV
Isosceles Triangle Theorem
B
Recall that an isosceles triangle is a triangle with two congruent sides.
The congruent sides are called the legs and the noncongruent side is called
the base. The angle formed by the two legs is called the vertex angle
A
while the two angles at each end of the base are called base angle.
What are the legs of the triangle? _____________ and ____________
What is the base side?__________________
What is the vertex angle? _________________
What are the base angles? ____________________ and ______________
Theorem 4.6 Isosceles Triangle Theorem (ITT)
If two sides of a triangle are congruent then the angles opposite those sides are congruent.
In the figure above,  _____   _____ .
Theorem 4.7 Converse of the Isosceles Triangle Theorem (ITTC)
If two angle of a triangle are congruent, then the sides opposite those angles are congruent.
Examples: Solve for x.
38°
116
2x - 11
x°
x°
2x + 5
(6x + 11)°
3x + 6
(8x – 12)°
5x – 15
Example: In ABC , mABC  45 and BA  BC . Classify ABC according to its angles and sides
C