Pearson Geometry Common Core, 2011
PG
Pearson Geometry Common Core, 2011 View details
Chapter Test
Continue to next subchapter

Exercise 11 Page 425

What criteria need to be met for a quadrilateral to be a rectangle?

x^(∘)=100^(∘)
y^(∘)=50^(∘)
z^(∘)=40^(∘)

Practice makes perfect

Let's take a look at the given figure. Notice that the quadrilateral has two pairs of parallel sides and one right angle.

The related theorem states that if a quadrilateral has two pairs of parallel sides and one right angle, it is a rectangle. Now, notice that the angles measuring 80^(∘) and x^(∘) are supplementary. This means that their measures add up to 180^(∘). x^(∘)+80^(∘)=180^(∘) ⇕ x^(∘)=100^(∘)

Also notice that in a rectangle, the bisecting diagonals divide it into four isosceles triangles. Therefore, if we consider the lower triangle with one of the angle measures equal to y^(∘), the other base angle measure is also y^(∘).

The remaining angle is vertical to the 80^(∘) angle, so the two angles are congruent.

To find the value of y^(∘), we apply the Triangle Angle Sum Theorem to this particular triangle. The theorem states that the angle measures of a triangle add up to 180^(∘).
y^(∘)+y^(∘)+80^(∘)=180^(∘)
2y^(∘)+80^(∘)=180^(∘)
2y^(∘)=100^(∘)
y^(∘)=50^(∘)
To find the value of z^(∘), we will first consider the diagonal of the rectangle. The diagonal lies on the transversal between the two parallel lines. By the Alternate Interior Angles Theorem, the alternate interior angles are the same measure.

Angle z^(∘) and 50^(∘) are complementary, meaning that their measures add up to 90^(∘). z^(∘)+50^(∘)=90^(∘) ⇔ z^(∘)=40^(∘) Now that we have found the value of z^(∘), we can summarize our findings. We found that x^(∘)=100^(∘), y^(∘)=50^(∘), and z^(∘)=40^(∘).