Big Ideas Math Geometry, 2014
BI
Big Ideas Math Geometry, 2014 View details
Quiz
Continue to next subchapter

Exercise 22 Page 386

Practice makes perfect
a Let's consider the given diagram.
We know that JKLM is a parallelogram. To list all congruent sides and angles in parallelogram JKLM, we will recall two theorems describing the properties of parallelograms.

Congruent Sides

The Parallelogram Opposite Sides Theorem states that the opposite sides of a parallelogram are congruent.

We have two pairs of congruent sides, JK≅ LM and JM≅ KL.

Congruent Angles

The Parallelogram Opposite Angles Theorem states that the opposite angles of a parallelogram are congruent.

We have two pairs of congruent angles, m∠ KJM≅ m∠ KLM and m∠ JML≅ m∠ JKL.

b The Opposite Sides Parallel and Congruent Theorem states that if one pair of opposite sides of a quadrilateral are congruent and parallel, then the quadrilateral is a parallelogram. Let's consider the quadrilateral QRST.

We know that QT∥RS and QT=RS. In other words, sides QT and RS of the quadrilateral are parallel and congruent.

We can see that QT and RS are opposite sides of quadrilateral QRST. Since they are also parallel and congruent, by the Opposite Sides Parallel and Congruent Theorem QRST is a parallelogram.

c From Part B we know that QRST is a parallelogram. Thus, we will use the properties of parallelograms to determine ST and the measures of the given angles. Let's do it one at a time.

Finding ST

Recall that by the Parallelogram Opposite Sides Theorem the opposite sides of a parallelogram are congruent, which means that they have the same measure.

The opposite sides ST and QR are congruent, ST≅QR. This means that ST=QR. We also know that QR= 3ft.

ST=QR QR= 3ft ⇒ ST= 3ft The side ST is 3feet long.

Finding m∠ QTS

Recall that by the Parallelogram Opposite Angles Theorem the opposite angles of a parallelogram are congruent.

The opposite angles ∠ QTS and ∠ QRS are congruent, ∠ QTS≅∠ QRS. This means that m∠ QTS=m∠ QRS. We also know that m∠ QRS=123^(∘). m∠ QTS=m∠ QRS m∠ QRS=123^(∘) ⇓ m∠ QTS=123^(∘) The angle ∠ QTS measures 123^(∘).

Finding m∠ TQR and m∠ TSR

Let's begin by finding m∠ TQR. Recall that the Parallelogram Consecutive Angles Theorem states that the consecutive angles of a parallelogram are supplementary. Since angles ∠ TQR and ∠ QRS are consecutive, we can write the following. m∠ TQR+m∠ QRS=180^(∘) We know that m∠ QRS=123^(∘). Let's substitute this value into the obtained expression and determine m∠ TQR.
m∠ TQR+m∠ QRS=180^(∘)
m∠ TQR+123^(∘)=180^(∘)
m∠ TQR=57^(∘)
The angle ∠ TQR measures 57^(∘). Note that by the Parallelogram Opposite Angles Theorem m∠ TSR=m∠ TQR. m∠ TSR=m∠ TQR m∠ TQR=57^(∘) ⇓ m∠ TSR=57^(∘) The angle ∠ TSR measures 57^(∘).