Pearson Geometry Common Core, 2011
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Pearson Geometry Common Core, 2011 View details
5. Law of Sines
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Exercise 9 Page 525

The Law of Sines relates the sine of each angle to the length of the opposite side.

x=2.1 and y=3.6

Practice makes perfect

For any △ ABC, let the lengths of the sides opposite to angles A, B, and C be a, b, and c, respectively.

The Law of Sines relates the sine of each angle to the length of the opposite side. sin A/a=sin B/b=sin C/c

Let's use this law to find the values of x and y. We will find them one at a time.

Finding x

Consider the given triangle.

We know that the length of a side is 5 and that the measure of its opposite angle is 119^(∘). We also know that the measure of the angle that is opposite to the side we want to find is 22^(∘). With this information and using the Law of Sines, we can write an equation in terms of x. sin 119^(∘)/5=sin 22^(∘)/x Let's solve our equation!
sin 119^(∘)/5=sin 22^(∘)/x
sin 119^(∘)* x=sin 22^(∘)* 5
x=sin 22^(∘)*5/sin 119^(∘)
x=2.141539...
x=2.1

Finding y

In order to obtain the value of y, we will first have to find the third interior angle using the Triangle Angle Sum Theorem. 180^(∘)- 119^(∘)- 22^(∘)= 39^(∘) Consider the triangle with the new information.

We know that the length of a side is 5 and that the measure of its opposite angle is 119^(∘). We want to find the length of the side that is opposite to the angle whose measure is 39^(∘). We can use the Law of Sines again! sin 119^(∘)/5=sin 39^(∘)/y Let's solve the above equation for y using the Cross Product Property.
sin 119^(∘)/5=sin 39^(∘)/y
sin 119^(∘)* y=sin 39^(∘)* 5
y=sin 39^(∘)*5/sin 119^(∘)
y=3.597680...
y=3.6