Big Ideas Math Geometry, 2014
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Big Ideas Math Geometry, 2014 View details
3. Using Chords
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Exercise 20 Page 550

Begin by identifying each arc measure. Consider the Congruent Corresponding Chords Theorem (Theorem 10.6).

See solution.

Practice makes perfect

We have been told that all the arcs in ⊙ P have integer measures.

Using this information, we will prove that x must be even. We will begin by identifying each arc measure. Since ∠ APB is the central angle of AB, the measure of AB is also x^(∘). mAB=x^(∘)

Next, let's recall the Congruent Corresponding Chords Theorem (Theorem 10.6) to talk about the measure of AC and BC.

Congruent Corresponding Chords Theorem

In the same circle or congruent circles, two minor arcs are congruent if and only if their corresponding chords are congruent.

By this theorem, we can conclude that AC and BC are congruent. Remember that congruent arcs have the same measure, so let's suppose they measure y ^(∘). mAC=mBC= y^(∘) Knowing that the measure of the entire circle is 360^(∘), we will write x in terms of y. x+ y+ y=360 ⇔ x=360- 2y Note that any integer that can be divided by 2 is an even number. Therefore, both 360 and 2y are even numbers. x=360_(even)-2y_(even) Since subtracting an even number from an even number always results in an even number, x must also be an even number.