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 6 Page 106

Can you think of a relationship between ∠ 4 and ∠ 6?

96^(∘), see solution.

Practice makes perfect

We want to find the measure of ∠ 6. Let's take a look at the photo of a portion of an airport.

Airport
Note that ∠ 3 and ∠ 4 form a straight line which means that they are supplementary angles. Therefore, their measures add up to 180^(∘). ∠ 3 +∠ 4=180^(∘) We know that the measure of ∠ 4 is 84^(∘). We can use this fact to find the measure of ∠ 3. Let's substitute 84^(∘) for ∠ 4 in our equation.
∠ 3 + ∠ 4 =180^(∘)
∠ 3 + 84^(∘)=180^(∘)
∠ 3= 96^(∘)
Next, notice that ∠ 3 and ∠ 6 lie outside lines a and b on opposite sides of the transversal, so they are alternate exterior angles. Because lines a and b are parallel, ∠ 3 and ∠ 6 are congruent. This means that the measure of ∠ 6 is 96^(∘).

Extra

Types of Angle Pairs

There are different types of angle pairs. We will describe them using the example graph of two lines intersected by a transversal.

Now we will list all of the types of angle pairs together with their definitions and corresponding examples.

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