McGraw Hill Glencoe Algebra 2, 2012
MH
McGraw Hill Glencoe Algebra 2, 2012 View details
1. Trigonometric Functions in Right Triangles
Continue to next subchapter

Exercise 39 Page 796

Determine the trigonometric ratio to be used according to the information that is given.

x = 19.3, y = 70.7

Practice makes perfect

We are given the lengths of one leg and the hypotenuse in a right triangle. We will find the missing measures of angles one at a time.

Value of x

We can find the value of x using the sine ratio.

The sine of the angle is the ratio between the lengths of the opposite side and the hypotenuse. sin x^(∘) = Length of leg opposite to the x^(∘) angle/Length of hypotenuse In our triangle, we have that the length of the opposite leg to the x^(∘) angle is 26 34 and the length of the hypotenuse is 81.

sin x^(∘) = opposite/hypotenuse
sin x^(∘) = 26 34/81
sin x^(∘) = 26.75/81
sin x^(∘) = 107/324

The sine of the angle is 107324. Now, to isolate x^(∘) we will use the inverse function of sin. sin x^(∘)=107/324 ⇔ x^(∘)=sin ^(- 1)107/324 Let's use a calculator to find the value of sin ^(- 1) 107324. First, we will set our calculator into degree mode. To do so, we need to push MODE, select Degree instead of Radian in the third row, and push ENTER. Next, we push 2ND followed by SIN, introduce the value 107324, and press ENTER.

The image could not be loaded
The image could not be loaded

The value of x^(∘) is about 19.3^(∘).

Value of y

We can find the value of y using the cosine ratio.

The cosine of the angle is the ratio between the lengths of the adjacent side and the hypotenuse. cos y = Length of leg adjacent to they^(∘)angle/Length of hypotenuse In our triangle, we have that the length of the adjacent leg to the y^(∘) angle is 26 34 and the length of the hypotenuse is 81.

cos y^(∘) = adjacent/hypotenuse
cos y^(∘) = 26 34/81
cos y^(∘) = 26.75/81
cos y^(∘) = 107/324

The cosine of the angle is 107324. Now, to isolate y^(∘) we will use the inverse function of cos. cos y^(∘)=107/324 ⇔ y^(∘)=cos ^(- 1)107/324 Similar as before, we will use a calculator to find the value of cos ^(- 1) 107324. Let's do it!

The image could not be loaded

The value of y^(∘) is about 70.7^(∘).