Pearson Geometry Common Core, 2011
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Pearson Geometry Common Core, 2011 View details
Chapter Review
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Exercise 19 Page 482

Analyze the given lengths and use the Right Triangle Altitude Theorem and its corollaries to write a proportion.

x=6sqrt(2)
y=6sqrt(6)

Practice makes perfect

We want to find the values of the variables x and y. To do so, we will use the corollaries of the Right Triangle Altitude Theorem.

Let's do it, separately.

Value of x

Let's analyze the given right triangle and recall the corollary that says that the length of the altitude to the hypotenuse of a right triangle is the geometric mean of the lengths of the segments of the hypotenuse.
Let's compare the theorem's corollary to the expressions in our figure. In our case, x is the altitude of the triangle, 12 and 6 are the lengths of partial segments of the hypotenuse. AD/DC=DC/DB ⇔ 12/x=x/6 Now we can use the Cross Product Property to find the value of x.
12/x=x/6
12 * 6 = x * x
â–Ľ
Solve for x
72 = x^2
x^2 = 72
sqrt(x^2) = sqrt(72)
|x| = ±sqrt(72)
|x| = ±sqrt(36*2)
|x| = ±sqrt(6^2*2)
|x| = ±sqrt(6^2)*sqrt(2)
|x| = ±6sqrt(2)

x ≥ 0

x = 6sqrt(2)

Value of y

We know the length of the hypotenuse, the value for the length of a segment of the hypotenuse, and the value for the length of the leg adjacent to this segment. Therefore, we can use a corollary of the Right Triangle Altitude Theorem to write a proportion.

Let's compare the theorem's corollary to the expressions in our figure. In our case, 12+6 is the length of the hypotenuse, 12 is the length of a partial segment of the hypotenuse, and y is the length of the leg that is adjacent to the partial segment. AB/CB=CB/DB ⇔ 12+6/y=y/12 Now we can use the Cross Product Property to find the value of x.
12+6/y=y/12
(12+6) * 6 = y * y
â–Ľ
Solve for y
18 * 12 = y * y
216 = y^2
y^2 = 216
sqrt(y^2) = sqrt(216)
|y| = ±sqrt(216)
|y| = ±sqrt(36*6)
|y| = ±sqrt(6^2*6)
|y| = ±sqrt(6^2)*sqrt(6)
|y| = ±6sqrt(6)

x ≥ 0

y = 6sqrt(6)