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 28 Page 645

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

x=13sqrt(2)/2, y=45

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 x

We are given that ∠ ABC is a right angle and that AB and BC are congruent. Therefore, △ ABC is a 45^(∘) - 45 ^(∘) - 90 ^(∘) triangle. We also know that the length of the hypotenuse AC is 13. By the 45^(∘) - 45 ^(∘) - 90 ^(∘) Triangle Theorem, we know the hypotenuse is sqrt(2) times the length of a leg, x. 13=sqrt(2)* x To find x, let's solve the above equation.
13=sqrt(2)* x
Solve for x
13/sqrt(2)=x
13sqrt(2)/sqrt(2)* sqrt(2)=x
13sqrt(2)/2=x
x=13sqrt(2)/2

Finding y

We are given that ∠ ABC is a right angle, and all of the sides in the polygon ABCD are equal. Therefore, the polygon is a square. Through the process of finding x, we know that the measure of ∠ BAC and ∠ ACB is 45 ^(∘).

Because polygon ABCD is a square, we know that ∠ BAD is a right angle. Therefore, ∠ CAD and ∠ BAC are complementary. Knowing the measure of ∠ BAC equals 45^(∘), we can find the value of y. 90=45+y ⇔ y=45