Download Day 2 Isosceles Triangles mt3.notebook

Day 2 Isosceles Triangles mt3.notebook
October 21, 2013
Review
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80
The point where the three medians meet is called the centroid of the triangle. The centriod is always inside the triangle. ­The centroid is also called the center of gravity.
Day 2 Isosceles Triangles mt3.notebook
October 21, 2013
Isosceles Triangles ...section 4­9 in your book
.
Isosceles Theorem: If two sides of a
triangle are ≅, then the angles opposite them
are also ≅.
* Converse is also true *
Converse of the Isosceles Triangle Theorem: If two angles of a triangle are congruent, then the sides opposite them are also congruent.
Vertex Angle: the angle created by the two congruent sides in an isosceles triangle.
(
(
Base: side across from the vertex in an isosceles triangle
Base angles: angles across from the congruent sides in an isosceles triangle
Day 2 Isosceles Triangles mt3.notebook
October 21, 2013
Example 1
If < X is the vertex angle of an isosceles triangle and m < X = 52,
find m < Y and m < Z.
X
Y
Z
Example 2
D
E
< D is the vertex angle of isosceles triangle DEF.
m < E = 4x
m < F = 3x + 16
Find x and the measure of angle D.
F
Day 2 Isosceles Triangles mt3.notebook
October 21, 2013
Example 3
Find x.
4x ­ 20
3x
Example 4
(
Find x and the length of the sides given.
3x
(
x + 10
Day 2 Isosceles Triangles mt3.notebook
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October 21, 2013