Core Connections Geometry, 2013
CC
Core Connections Geometry, 2013 View details
3. Section 2.3
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Exercise 116 Page 134

Practice makes perfect
a By the Triangle Sum Theorem, we know that the three angle measures of a triangle sum to 180^(∘). With this, we can write an equation.
(3x-2^(∘))+(x+8^(∘))+(2x+3^(∘))=180^(∘) Let's solve for x in this equation.
(3x-2)+(x+8)+(2x+3)=180
3x-2+x+8+2x+3=180
6x+9=180
6x=171
x=28.5
b Examining the diagram, we notice that the two angles are alternate exterior angles. Since the two lines cut by the transversal are parallel, we know by the Alternate Exterior Angles Theorem that these angles are congruent. This means we can equate their expressions.
6x-28^(∘)=4x+18^(∘) Let's solve this equation for x.
6x-28=4x+18
2x-28=18
2x=46
x=23
c Notice that the triangle is isosceles which means it has two congruent legs. By the Base Angles Theorem, we know that the base angles are congruent. Let's call these angles y and add them to the diagram.
Let's isolate a few parts of the diagram.

Here, we see that y and 56^(∘) are corresponding angles and since the two lines cut by the transversal are parallel, we know by the Corresponding Angles Theorem that they are congruent. Therefore, we can say that y=56^(∘). Let's add this information to the diagram.

Finally, we can by the Triangle Sum Theorem, write an equation including x. x+56^(∘)+56^(∘) = 180^(∘) Let's solve this equation for x.
x+56+56 = 180
x+112 = 180
x= 68