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Oct 27:34 AM
These people need to take their Constructions Test. Here are your only options:1. Today right after school2. Tomorrow Aca Prep3. Tomorrow after school
P. 3Jordan B.Marissa C.Michael D. Victoria M.Madison R.
P.4 Ashleigh S.Chloee S.Karina M.Kaitlyn M.Amber L.Nick K.Tatum B.
P.6Jodi F.Bryce H.Mary T.Kim AChristina A,
Oct 27:38 AM
Oct 27:38 AM Jul 249:36 AM
3.4 Triangle Angle Theorems
I CAN...Apply the Triangle AngleSum Theorem and Exterior Angle Theorem
Jul 249:36 AM
Triangle AngleSum Theorem
The sum of the measures of the angles of a triangle is 180.
Ex) m∠A + m∠B + m∠C = 180.
A
B
C
Jul 249:36 AM
Triangle AngleSum Theorem Example
The diagram shows the path of the softball in a drill developed by four players. Find the measure of each numbered angle.
What relationships do you recognize in the figure?
What is a good course of action to solve this problem?
2
Jul 249:36 AM
Triangle AngleSum Theorem Example
Step 1) Find m∠1. (Triangle AngleSum Thm.)
m∠1+ 43 + 74 = 180
m∠1+ 117 = 180
m∠1 = 63
Jul 249:36 AM
Triangle AngleSum Theorem Example
Step 2) Find m∠2. (Vertical Angles are Congruent)
m∠1 = m∠2
m∠1 = 63
m∠2 = 63
Jul 249:36 AM
Triangle AngleSum Theorem Example
Step 3) Find m∠3. (Triangle AngleSum Thm.)
m∠3 + 63 + 79 = 180
m∠3 + 142 = 180
m∠3 = 38
Answers
Jul 249:36 AM
Triangle AngleSum Theorem Proof
Jul 249:36 AM
1. AC DB2. m∠4 + m∠3 + m∠5 = 180.3. m∠1 = m∠44. m∠2 = m∠55. m∠1 + m∠2 + m∠3 = 180.
Statements Reasons1. Given2. Straight Angles Equal 180 degrees.3. Alt. Int. Angles are ≅ 4. Alt. Int. Angles are ≅ 5. Substitution Property
Triangle AngleSum TheoremProof Practice
A
B
C
D54 3
21Given: AC DBProve: m∠1 + m∠2 + m∠3 = 180.
Jul 249:36 AM
An Exterior Angle is...
An angle formed by one side of a triangle and the extension of another side.
Remote Interior Angles are...
The angles of a triangle that are not adjacent to a given exterior angle.
12
3Exterior Angle
Remote InteriorAngles
3
Jul 249:36 AM
Exterior Angle Theorem
The measure of an exterior angle of a triangle is equal to the sum of the measures of the two remote interior
angles.
Ex) m∠A + m∠B = m∠11
A
B
C
Jul 249:36 AM
Exterior Angle Theorem Proof
Jul 249:36 AM
Exterior Angle Theorem Example 1
Find the measure of ∠FLW in the fenced flower garden shown.
Jul 249:36 AM
Exterior Angle Theorem Example 1Set up equation and solvefor x.(Exterior Angle Theorem)
m∠LOW + m∠OWL = m∠FLW
x + 32 = 2x – 48
32= x – 48
80= x
Answers
Jul 249:36 AM
Exterior Angle Theorem Example 2
The piece of quilt fabric is in the shape of a right triangle. Find the measure of ∠ACD.
Answers
Oct 27:39 AM
4
Jul 249:36 AM
Triangle AngleSum Theorem Corollaries
Corollary A statement that can be easily proved using a theorem is called a corollary of that theorem.
1) The acute angles of a right triangle are complementaryex) m∠A + m∠B = 90
2) There can be at most one right or obtuse angle in a triangle.
A
C B
Jul 249:36 AM
Triangle Angle Example 1
Find the measure of each numbered angle.
What relationships do you recognize in the figure?
What is a good course of action to solve this problem?
Jul 249:36 AM
Triangle Angle Example 1
Step 1) Find m∠1.(Exterior Angle Thm)
m∠1 = 48 + 56
= 104
Step 2) Find m∠2. (Linear Pair)
m∠1 + m∠2 = 180
104 + m∠2 = 180
m∠2 = 76
Jul 249:36 AM
Triangle Angle Example 1
Step 3) Find m∠3.(Complementary Angles)
m∠ 3 = 90 48
= 42
Step 4) Find m∠4. (Triangle AngleSum Thm)
(90 – 34) + m∠2 + m∠ 4 = 180
56 + 76 + m∠ 4 = 180
132 + m∠4 = 180
m∠4 = 48
Jul 249:36 AM
Triangle Angle Example 1
Step 5) Find m∠5.(Triangle Angle Sum Thm)
m∠5 + 41 + 90 = 180
m∠5 + 131 = 180
m∠5 = 49
Answers
Jul 249:36 AM
Triangle Angle Example 2
Find m∠3.
Answers
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Sep 307:40 PM