McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
5. Tangents
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Exercise 23 Page 755

Practice makes perfect
a We are given that in the drawn arbor AC and BC are tangents to ∘ D. We also know that the radius of the circle is 26 inches and EC= 20 inches. Let's take a look at the given diagram.
Recall that the tangent is perpendicular to the radius at the tangency point. This means that ∠ A is a right angle.
As we can see, △ ADC is a right triangle. Therefore we can find AC using the Pythagorean Theorem. According to this theorem the sum of the squared legs of a right triangle is equal to its squared hypotenuse. AD^2+AC^2=DC^2 Let's solve the above equation by substituting the appropriate segment lengths. Notice that DC= 26+ 20=46 inches. Also, since AC represents a length we will consider only the positive case when taking the square root of AC^2.
AD^2+AC^2=DC^2
26^2+AC^2=46^2
676+AC^2=2116
AC^2=1440
sqrt(LHS)=sqrt(RHS)
sqrt(AC^2)=sqrt(1440)
AC=sqrt(1440)
AC=37.9473...
AC≈ 37.95
The length of AC is approximately 37.95 inches.
b In this part we are asked to find BC. Let's look at the diagram.

Remember that if two segments from the same exterior point are tangent to a circle, then they are congruent. This means that AC=BC. Since we found in the previous part that AC is approximately 37.95 inches, BC is also 37.95 inches.