Big Ideas Math: Modeling Real Life, Grade 8
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Big Ideas Math: Modeling Real Life, Grade 8 View details
1. Parallel Lines and Transversals
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Exercise 21 Page 109

Can you spot any pairs of angles with equal measures?

129.5^(∘), see solution.

Practice makes perfect

Let's review what we know about different types of angle pairs. We will use the graph below as an example.

Now let's take a look at the different types of angle pairs and their definitions.

Pairs of Angles
Type Definition Example
Supplementary Angles Together, they form a straight line and their measures add up to 180^(∘). ∠ 1 and ∠ 3
Corresponding Angles They lie in corresponding positions on the same side of the transversal. ∠ 1 and ∠ 5
Vertical Angles They lie on the opposite sides of the point of intersection of two lines. ∠ 1 and ∠ 4
Alternate Interior Angles They lie between the two lines on opposite sides of the transversal. ∠ 4 and ∠ 5
Alternate Exterior Angles They lie outside the two lines on opposite sides of the transversal. ∠ 2 and ∠ 7

We are asked to complete the following statement.

If the measure of ∠ 7 = 50.5^(∘), then the measure of ∠ 6 = .

First, let's take a look at the given graph. We know that the measure of ∠ 7 is 50.5^(∘).

Note that ∠ 7 and ∠ 3 form a straight line. Therefore they are supplementary angles and their measures add up to 180^(∘) . 50.5^(∘)+∠ 3 =180^(∘) ⇕ ∠ 3 = 129.5^(∘) The measure of ∠ 3 is 129.5^(∘). Next, let's notice that lines a and b are parallel and cut by the transversal c. We will use this fact to find the measure of ∠ 6.

We can see that ∠ 3 and ∠ 6 are corresponding angles. Corresponding angles are congruent, which means that the measure of ∠ 6 is also 129.5^(∘). Let's complete our statement.

If the measure of ∠ 7 = 50.5^(∘), then the measure of ∠ 6 = 129.5^(∘).