Core Connections Geometry, 2013
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Core Connections Geometry, 2013 View details
1. Section 12.1
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Exercise 26 Page 739

Practice makes perfect
a To determine x, we should first recognize that the angles from the diagram are vertical angles. This means that they are congruent by the Vertical Angles Theorem.
We can equate the expressions for the two angle measures and solve for x.
4x-2^(∘) = 2x+9^(∘)
Solve for x
2x-2^(∘) =9^(∘)
2x =11^(∘)
x=5.5^(∘)
b Let's consider the given diagram.
he diagram depicts a quadrilateral along with measures of its interior angles. Now, recall the Polygon Angle-Sum Theorem.

Polygon Angle-Sum Theorem

The sum of the measures of the interior angles of a convex n-gon is (n-2)*180^(∘).

In this case, expressions are given for the measures of the interior angles. We can write an equation where the sum of these expressions is equal to (n-2)180. 116^(∘) + 3x+8^(∘) + 32^(∘) + 2x-1^(∘)= (n-2)180 Our polygon has 4 sides, so we can substitute 4 for n. 116^(∘) + 3x+8^(∘) + 32^(∘) + 2x-1^(∘) = (4-2)180^(∘) Finally, let's solve the equation above for x.
116^(∘) + 3x+8^(∘) + 32^(∘) + 2x-1^(∘) = (4-2)180^(∘)
5x + 155^(∘) = 2(180^(∘))
5x + 155^(∘) = 360^(∘)
5x = 205^(∘)
x = 41^(∘)
c The following diagram is given.
To find the value of x, we will need to use the Corresponding Angles Theorem.

Corresponding Angles Theorem

If a transversal intersects two parallel lines, then corresponding angles are congruent.

We can visualize this theorem. Consider two lines l and m, where l∥ m.

This allows us to find the measure of one of the angles with which the leftmost one forms a linear pair.

The measures of angles forming a linear pair must sum to 180^(∘). This allows us to write the following equation. 7x-3^(∘) + 4x+12^(∘) = 180^(∘) Let's solve this equation for x.
7x-3^(∘) + 4x + 12^(∘) = 180^(∘)
11x + 9^(∘) = 180^(∘)
11x = 171^(∘)
x = 171/11^(∘)