Lesson Lesson 6-46-4

Isosceles Isosceles TrianglesTriangles

Ohio Content Ohio Content Standards:Standards:

Ohio Content Ohio Content Standards:Standards:

Formally define geometric figures.

Ohio Content Ohio Content Standards: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:

Isosceles Triangle:Isosceles Triangle:

A triangle that has a least two congruent sides.

Isosceles Triangle:Isosceles Triangle:

The congruent sides are called legslegs.

Isosceles Triangle:Isosceles Triangle:

The side opposite the vertex angle is called

the basebase.

Isosceles Triangle:Isosceles Triangle:Vertex Angle

LegLeg

Base

Base Angles

Theorem 6-2Theorem 6-2Isosceles Triangle Isosceles Triangle

TheoremTheorem

Theorem 6-2Theorem 6-2Isosceles Triangle Isosceles Triangle

TheoremTheorem

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 6-4Theorem 6-4Converse of Isosceles Converse of Isosceles

Triangle TheoremTriangle Theorem

Theorem 6-4Theorem 6-4Converse of Isosceles Converse of Isosceles

Triangle TheoremTriangle Theorem

If two angles of a triangle are congruent, then the

sides opposite those angles are congruent.

D1

2

E

F

3x - 3

2x + 2

. and , , Find

.281 and 21 ,In

EFDFFm

mDEF

Assignment:Assignment:

Pgs. 249 – 250Pgs. 249 – 2506-14 all6-14 all19-21 all19-21 all