McGraw Hill Glencoe Geometry, 2012
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McGraw Hill Glencoe Geometry, 2012 View details
4. Trigonometry
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Exercise 51 Page 575

Evaluate the lengths of the missing sides using the sine and the tangent.

Perimeter: Approximately 13.83in.
Area: Approximately 7.50in.^2

Practice makes perfect

We are asked to find the perimeter and the area of the given right triangle. To do this, we need to find the lengths of the missing sides. Let's call them x and y.

Since we are given an angle measure of this triangle, we can use the trigonometric ratios to evaluate the lengths of missing sides. Let's begin with recalling the definition of the tangent of an angle. If△ ABCis a right triangle with acute∠ A, then the tangent of∠ Ais the ratio of the length of the leg opposite∠ A to the length of the leg adjacent∠ A.

Using this information, we can write an equation to find the value of x. The leg opposite ∠ 59^(∘) is 5 and the leg adjacent to ∠ 59^(∘) is x. tan 59^(∘)=5/x Let's solve this equation.
tan 59^(∘)=5/x
x*tan 59^(∘)=5
x=5/tan 59^(∘)
x=3.0054...
x≈ 3
The value of x is approximately 3. To find the value of y, let's recall the definition of the sine of an angle. If△ ABCis a right triangle with acute∠ A, then the sine of∠ Ais the ratio of the length of the leg opposite∠ Ato the length of the hypotenuse.
This means that the sine of ∠ 59^(∘) is the ratio of the length of the leg opposite ∠ 59^(∘), which is 5, to the length of the hypotenuse, y. sin59^(∘)=5/y Next, we will solve the equation.
sin 59^(∘)=5/y
y*sin 59^(∘)=5
y=5/sin 59^(∘)
y=5.8331...
y≈ 5.83
Now we have all side lengths of this triangle.

Finally, we will evaluate the perimeter and the area of this triangle. Remember that, since we will use approximate values, the perimeter and the area will also be approximations. First recall that the perimeter of the figure is the sum of all its sides lengths. Perimeter: 3+ 5.83+ 5=13.83 The perimeter of the triangle is approximately 13.83 inches. Next, let's recall that the area of a right triangle is half of the product of its legs. Area: 1/2* 3* 5=7.5 The area of the triangle is approximately 7.5 square inches.