McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
3. Special Right Triangles
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Exercise 29 Page 645

In the given figure, you can find a 45^(∘)- 45 ^(∘) - 90 ^(∘) triangle.

x=3sqrt(2), y=6sqrt(2)

Practice makes perfect

Let's begin by reviewing the properties of special right triangles.

45^(∘) - 45 ^(∘) - 90 ^(∘) Triangle
In a 45^(∘) - 45 ^(∘) - 90 ^(∘) triangle, the legs l are congruent and the hypotenuse h is sqrt(2) times the length of a leg.
30 ^(∘) - 60 ^(∘) - 90 ^(∘) Triangle
In a 30 ^(∘) - 60 ^(∘) - 90 ^(∘) triangle, the hypotenuse h is 2 times the length of the shorter leg s and the longer leg l is sqrt(3) times the length of the shorter leg.

Let's name the vertices of the given figure. Then we can find y and x, one at a time.

Finding y

We are given that ∠ ABC is a right angle and that the measure of ∠ ACB is 45^(∘). Therefore, by the Triangle Angle Sum Theorem, the measure of ∠ BAC must also be 45^(∘). This means, △ ABC is a 45^(∘) - 45 ^(∘) - 90 ^(∘) triangle. In such triangle, the hypotenuse is sqrt(2) times the length of a leg. Knowing that, we can find the value of y. y= sqrt(2) * 6 ⇔ y=6sqrt(2)

Finding x

We are given that ∠ BDC is a right angle, and the measure of ∠ ACB is 45 ^(∘). Again, by the Triangle Angle Sum Theorem, the measure of ∠ CBD must also be 45^(∘), which means △ BCD is a 45^(∘) - 45 ^(∘) - 90 ^(∘) triangle. Let's add the information to our diagram.

The length of the leg is x and the length of the hypotenuse is 6. By the 45^(∘) - 45 ^(∘) - 90 ^(∘) Triangle Theorem, the length of the hypotenuse is sqrt(2) times the length of a leg, x.

6= sqrt(2) * x
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Solve for x
6/sqrt(2)=x
6sqrt(2)/sqrt(2)* sqrt(2)=x
6sqrt(2)/2=x
3sqrt(2)=x
x=3sqrt(2)