McGraw Hill Glencoe Geometry, 2012
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McGraw Hill Glencoe Geometry, 2012 View details
3. Special Right Triangles
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Exercise 33 Page 563

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

x=45, y=12sqrt(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 ∠ ADC is a right angle, and sides AB and AD are equal. Therefore, the polygon ABCD is a square, which means all of the sides are equal. Let's add this information to our diagram.

Because polygon ABCD is a square, we know that ∠ BAD is a right angle and that sides AB and AD are congruent. Therefore, △ ABD is a 45^(∘) - 45 ^(∘) - 90 ^(∘) triangle. In such triangle, the hypotenuse is sqrt(2) times the length of a leg. With this information, we can find the value of y. y= sqrt(2) * 12 ⇔ y=12sqrt(2)

Finding x

Let's add the obtained information to the diagram.

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