Download Geometry Section 4.1 - West End Public Schools

Geometry
Section 4.1
Apply Triangle Sum Properties
Angles of a Triangle
• When the sides of a polygon
(triangle) are extended, other angles
are formed. The original angles are
the interior angles. The angles that
form linear pairs with the interior
angles are the exterior angles
Triangle Sum Theorem
• The sum of the
measures of the
interior angles is
180°
B
A
C
mA  mB  mC  180
Exterior Angle Theorem
• The measure of an
exterior triangle is
equal to the sum of
the measures of
the two
nonadjacent
interior angles
B
A
1
m1  mA  mBC
Corollary to the Triangle
Sum Theorem
• The acute angles
of a right triangle
are complementary
A
C
mA  mB  90
B
Examples
• Page 221 #15, 17, 33, 37
Assignment
• Section 4.1
• Page 221
• Problems #1-6 all, 8-18 even, 21-26,
32, 34