Big Ideas Math Geometry, 2014
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Big Ideas Math Geometry, 2014 View details
6. Segment Relationships in Circles
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Exercise 14 Page 573

x=1

Practice makes perfect

We are given the following diagram and asked to find the value of x.

To do this, we will use the Segments of Secants and Tangents Theorem. Let's recall what it states.

Segments of Secants and Tangents Theorem

If a secant segment and a tangent segment share an endpoint outside a circle, then the product of the lengths of the secant segment and its external segment equals the square of the length of the tangent segment.

First, we need to calculate the lengths of the secant NM by adding x and 2. NM=x+2 According to this theorem, the product of NM and PM is equal to the square of OM. NM* PM =OM^2 Let's substitute NM with x+2, PM with x, and OM with sqrt(3) and solve the equation for x.
NM* PM =OM^2
( x+2)( x) = sqrt(3)^2
(x+2)(x)=3
x^2+2x=3
This is a quadratic equation. Let's solve it by completing the square. Note that all terms with x are on one side of the equation, so we do not need to rewrite it. In this equation, b=2. Using this information, we can calculate ( b2 )^2.
( b/2 )^2
Substitute 2 for b and evaluate
( 2/2 )^2
1^2
1
Next, we will add ( b2 )^2=1 to both sides of our equation. Then, we will factor the trinomial on the left-hand side and solve the equation.
x^2+2x=3
Complete the square and Solve for x
x^2+2x+ 1=3+ 1
(x+1)^2=3+1
(x+1)^2=4
sqrt((x+1)^2)=sqrt(4)
x+1=± 2
x=- 1± 2
We conclude that the equation has two solutions. x_1&=- 1+2=1 x_2&=- 1-2=- 3 On the diagram x represents the distance PM, so it cannot have a negative value. Therefore, x is equal to 1.