McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
6. Secants, Tangents, and Angle Measures
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Exercise 24 Page 765

Where do the lines tangent to the circle intersect? After knowing this, use the corresponding formula.

y=80^(∘)

Practice makes perfect

Let's begin by drawing a diagram that illustrates the given situation.

We are given that x=260^(∘), which implies that m ADB is 260^(∘). Since CA and CB are tangent to the circle and they intersect each other outside it, we have that y is equal to one half the measure of the difference of the intercepted arcs. y = 1/2(m ADB - m AB) By using the measure of the major arc we will find the measure of the minor arc. m ADB^(260^(∘)) + m AB = 360^(∘) ⇓ m AB = 100^(∘) Finally, let's substitute the measures of both arcs to find the measure of the required angle.
y = 1/2(m ADB - m AB)
y = 1/2( 260^(∘) - 100^(∘))
Simplify
y = 1/2(160^(∘))
y = 160^(∘)/2
y=80^(∘)