Pearson Geometry Common Core, 2011
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Pearson Geometry Common Core, 2011 View details
2. Special Right Triangles
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Exercise 25 Page 504

Divide the given triangle into two right triangles. Do you have a 30^(∘)-60^(∘)-90^(∘) or a 45^(∘)-45^(∘)-90^(∘) triangle?

a=10sqrt(3), b=5sqrt(3), c=15, d=5

Practice makes perfect

Let's divide the given triangle into two right triangles.

We will deal with these triangles one at a time. Let's start with the second one.

Triangle 2

Notice that this is a right triangle with an acute angle that measures 60^(∘). Therefore, by the Triangle Angle Sum Theorem the measure of the third angle must be 30^(∘).
We have a 30^(∘)-60^(∘)-90^(∘) triangle. In this type of triangle, the length of the hypotenuse is twice the length of the shorter leg.
10 = 2 * d
Solve for d
5 = d
d = 5
We found that the length of the shorter leg is 5. Moreover, in a 30^(∘)-60^(∘)-90^(∘) triangle the length of the longer leg is sqrt(3) times the length of the shorter leg. This will let us find the value of b. b=sqrt(3)* 5 ⇔ b=5sqrt(3)

Triangle 1

The first right triangle has an angle that measures 30^(∘). Therefore, by the Triangle Angle Sum Theorem the measure of the third angle is 60^(∘). Remember, we already know that b=5sqrt(3).

Once again, we have a 30^(∘)-60^(∘)-90^(∘) triangle. In this type of triangle, the length of the hypotenuse is twice the length of the shorter leg. a= 2 * 5sqrt(3) ⇔ a=10sqrt(3) We found that the length of the hypotenuse is 10sqrt(3). Moreover, in a 30^(∘)-60^(∘)-90^(∘) triangle the length of the longer leg is sqrt(3) times the length of the shorter leg. This will let us find the value of c.
c=sqrt(3) * 5sqrt(3)
Simplify right-hand side
c=5*sqrt(3)*sqrt(3)
c=5*3
c=15