Topic/Objective: Section 4.1
Notes #22 Apply Triangle Sum Properties
Name:
Date:
Period:
Essential Question:
Questions:
triangle
scalene triangle
isosceles triangle
equilateral triangle
acute triangle
right triangle
obtuse triangle
equiangular triangle
Notes:
is a polygon with three sides.
has no congruent sides
has at least two congruent sides
has three congruent sides.
has three acute angles.
has one right angle.
has one obtuse angle
has three congruent angles
*****NOTE******* When the sides of a polygon 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.
Theorem 4.1 Triangle Sum The sum of the measures of the interior angles of a triangle is 180°.
Theorem:
Theorem 4.2 Exterior The measure of an exterior angle of a triangle is equal to the sum of the
Angle Theorem: measures of the two nonadjacent interior angles.
Corollary to the Triangle The acute angles of a right triangle are complementary.
Sum Theorem:
Example 1
Classify the triangle by its sides and by its angles.
Example 2
a
Find m∠ BAC and m∠ BCA.
Questions:
Notes:
b. Find m ∠ BCD and m∠ ABC.
Independent Practice
Classify the triangle by its sides and by its angles.
Find m∠ ABD and m∠ BDC.
Find m∠ CAB and m∠ CBA.
Summary:
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