Classifying Triangles

1
Classifying Triangles Angles of Triangles

• Sections 4-1 4-2

2

• A triangle is the figure formed by 3 segments
  joining 3 noncollinear points. Each of the 3
  points is a vertex. The segments are the sides.

A
B
C
3
Classifying Triangles by Sides

• Scalene Triangle
• no sides congruent

Isosceles Triangle At least 2 sides congruent
Equilateral Triangle All sides congruent
4
Classifying Triangles by Angles
700

• Acute 3 acute angles

500
600
Right 1 right angle
400
Obtuse one obtuse angle
200
1200
600
Equiangular all angles congruent
600
600
5
Parts of an Isosceles Triangle
vertex angle
leg
leg
base
base angles
6
Angle Sum Theorem

• The sum of the measures of the angles of a
  triangle is 180.

1000
400
400
7
Third Angle Theorem

• If 2 angles of one triangle are congruent to 2
  angles of another triangle, then the third angles
  are congruent.

8
Corollariesstatements that can be easily proved
using a theorem

• Each angle of an equiangular triangle has measure
  60.
• In a triangle, there can be at most one right
  angle or obtuse angle.
• The acute angles of a right triangle are
  complementary.

9
Exterior Angle Theorem

• The measure of an exterior angle of a triangle
  equals the sum of the measures of the 2 remote
  interior angles.

Remote interior angles
350
Exterior
750
400
10
Joke Time

• What has wings and solves number problems?
• A mothematician

11

• What did one math book say to the other math
  book?
• Dont bother me! Ive got my own problems!

12

• What would a math student say to a fat parrot?
• Poly-no-mial