Transcript 4.1 Triangles and Angles

Triangles and Angles
Classifying Triangles
Triangle Classification by Sides
Equilateral
Isosceles
Scalene
3 congruent sides
2 congruent sides
No congruent sides
Triangle Classification by Angles
Equilateral
Acute
Obtuse
60
20
80
60
60
70
40
40
3 congruent angles
3 acute angles
Right
35
1 right angle
90
55
120
1 obtuse angle
More Definitions

Interior Angles: angles
inside the triangle
(angles A, B, and C)
2
B
1
Exterior Angles:
angles adjacent to the
interior angles
(angles 1, 2, and 3)

A
C
3
Triangle Sum Theorem

The sum of the
measures of the
interior angles of a
triangle is 180o.
When you add all the
angles of a triangle
together, you get the
number 180.
<A + <B + <C = 180o
60 + 60 + 60 = 180o
40 + 80 + 40 = 180o
30 + 100 + x = 180o
100
80
B
60
A
60
40
30
60
40
50
C
Solving for The Angles
92
+ 42
x = 180
Write
the+ angles
addition
 with
134 +
x = 180signs
between-134
them.
 in
-134

 Write
X=46 = 180
 Combine Like
Terms
 Solve for x
 Substitute x back in
if you need to.


B
42
A
92





xC
Write the angles with addition signs in
between them.
Write = 180
Combine Like Terms
Solve for x
Substitute x back in if you need to.