Download 4.1 Triangles and Angles

Triangles-Classified by Sides
Equilateral Triangle
3 Congruent Sides
Isosceles Triangle
At least 2 congruent sides
Scalene Triangle
No congruent Sides
Triangles Classified by Angles
Acute Triangle
All angles acute
Right Triangle
1 Right Angle
Equiangular
3 congruent angles
Obtuse Triangle
1 Obtuse Angle
Ex. 1 Classify the Triangle
Ex. 2 Classify the Triangle
Parts of a Triangle
 Vertex:3 Points joining
the sides of a triangle
 Points A, B and C are the
vertices of the triangle to
the right
B
A
C
Parts of a right triangle
 Legs: The sides that form
the right angle
 Hypotenuse: The side
opposite of the right
angle
hypotenuse
leg
leg
Parts of an Isosceles Triangle
 Legs: The two congruent
sides
 Base: The third
remaining side
leg
leg
base
Interior Angles
Exterior Angles
Triangle Sum Theorem
 The sum of the measures of the interior angles of a
triangle is 180⁰
m A m B m C 180
B
A
C
Ex. 3 Find x
Ex. 4 Find x
Exterior Angle Theorem
 The measure of an exterior angle of a triangle is equal
to the sum of the measures of the two nonadjacent
interior angles
B
m 1 m A m B
1
A
C
Ex. 5 Find x