Download Lesson 6-4 - Elgin Local Schools

Lesson
6-4
Isosceles
Triangles
Ohio Content
Standards:
Ohio Content
Standards:
Formally define geometric figures.
Ohio Content
Standards:
Formally define and explain key aspects of
geometric figures, including:
a. interior and exterior angles of polygons;
b. segments related to triangles (median,
altitude, midsegment);
c. points of concurrency related to
triangles (centroid, incenter, orthocenter,
and circumcenter);
d. circles (radius, diameter, chord,
circumference, major arc, minor arc,
sector, segment, inscribed angle).
Isosceles Triangle:
Isosceles Triangle:
A triangle that has a least
two congruent sides.
Isosceles Triangle:
The congruent sides are
called legs.
Isosceles Triangle:
The side opposite the
vertex angle is called
the base.
Isosceles Triangle:
Vertex
Angle
Leg
Leg
Base
Angles
Base
Theorem 6-2
Isosceles Triangle
Theorem
Theorem 6-2
Isosceles Triangle
Theorem
If two sides of a triangle
are congruent, then the
angles opposite those sides
are congruent.
Find the values of the variables.
x°
y°
35°
45°
Theorem 6-4
Converse of Isosceles
Triangle Theorem
Theorem 6-4
Converse of Isosceles
Triangle Theorem
If two angles of a triangle
are congruent, then the
sides opposite those angles
are congruent.
In DEF , 1  2 and m1  28.
Find mF , DF , and EF .
E
2
3x - 3
1
D
F
2x + 2
Assignment:
Pgs. 249 – 250
6-14 all
19-21 all