Download Classifying Triangles by Sides

Geometry
Notes
Name_________________________
Applying Triangle Sum Properties
scalene
acute
Classifying Triangles by Sides
isosceles
equilateral
Classifying Triangles by Angles
right
obtuse
equiangular
B
Triangle Sum Theorem –
The sum of the interior angles of a triangle is 180°.
A
C
mA + mB + mC = 180
Example 1
Find the value of x in the diagram shown.
(2x + 4)
(3x - 5)
(2x - 1)
Example 2
Find the measure of the acute angles in the diagram shown.
2x
(x - 6)
B
Exterior Angle Theorem –
The measure of an exterior angle is equal to the sum
of the two nonadjacent interior angles.
1
A
C
m1 = mA + mB
J
Example 3
Find m  JKM.
x
70
(2x - 5)
L
K
M
Corollary to the Triangle Sum Theorem –
The acute angles of a right triangle are complementary.
Example 4
Find the measure of  1 in the diagram.
3x
1
40
Example 5
Find the value of x.
(5x - 10)
2x
(3x + 18)
42