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Transcript 
2.9 warm-up
When six students and two adults saw a
movie, the total ticket cost was $50. Adult
tickets cost twice as much as student
tickets. Which number sentence best
represents the situation ?
a. x+2x=50x
b. 6x+2=50
c. 6x+2(x/2)=50
d. 6x+2(2x)=50
10
2.9 warm-up
When six students and two adults saw a
movie, the total ticket cost was $50. Adult
tickets cost twice as much as student
tickets. Which number sentence best
represents the situation ?
a. x+2x=50x
b. 6x+2=50
c. 6x+2(x/2)=50
d. 6x+2(2x)=50
10
3.4 Parallel Lines
and the Triangle
Angle-Sum theorem
You will be able to
identify the different
types of triangles.
You will use parallel
lines to solve for
angles in a triangle
Pardekooper
Lets start with a theorem
• Triangle Angle-Sum Theorem
– The sum of the measures of the angles of
a triangle is 1800.
C
A + B + C = 1800
A
B
Pardekooper
How does it work ?
Combine like terms
Substitution
• Find the value of x for the following triangle.
C like terms
Combining
390
0
65
A
 -sum
A + B + C = 1800
substitution
65 + x + 39 = 180
simplify
x + 104 = 180
xTriangle
+ 104 -Angle-Sum
104 = 180 - 104 subtraction
x0
x = 76
B
simplify
subtraction
Pardekooper
Now, lets look at the different
types of triangles.
• Equiangular 
– All angles are congruent
Pardekooper
Now, lets look at the different
types of triangles.
• Equilateral 
– All sides are congruent
Pardekooper
Now, lets look at the different
types of triangles.
• Isosceles 
– Two sides are congruent
Pardekooper
Now, lets look at the different
types of triangles.
• Acute 
– All angles are less than 900
Pardekooper
Now, lets look at the different
types of triangles.
• Right 
– One angle is 900
Pardekooper
Now, lets look at the different
types of triangles.
• Obtuse 
– One angle is greater than 900
Pardekooper
Now, lets look at the different
types of triangles.
• Scalene 
– No sides are congruent
Pardekooper
Here are some terms
Exterior angle
of a polygon
Remote
interior
angles
Just one more theorem
• Triangle Exterior Angle Theorem
– The measure of each exterior angle of a triangle
equals the sum of the measure of its two remote
interior angles.
C
mA = mB + mC
A
B
Pardekooper
Lets try a problem.
700
1130
mA = mB + mC
113 = 70 + x
113 - 70 = 70 - 70 + x
43 = x
x0
 Exterior 
substitution
subtraction
simplify
Pardekooper
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