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4-1 Right Triangle Trigonometry
Find the exact values of the six trigonometric functions of θ.
3. SOLUTION: The length of the side opposite θ is 9, the length of the side adjacent to θ is 4, and the length of the hypotenuse is
.
7. SOLUTION: The length of the side opposite θ is 6 and the length of the hypotenuse is 10. By the Pythagorean Theorem, the
length of the side adjacent to θ is
= or 8.
Use the given trigonometric function value of the acute angle θ to find the exact values of the five
remaining trigonometric function values of θ.
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9. sin θ = SOLUTION: Page 1
4-1 Right Triangle Trigonometry
Use the given trigonometric function value of the acute angle θ to find the exact values of the five
remaining trigonometric function values of θ.
9. sin θ = SOLUTION: Draw a right triangle and label one acute angle θ. Because sin θ = = , label the opposite side 4 and the
hypotenuse 5.
By the Pythagorean Theorem, the length of the side adjacent to θ is
or 3.
15. cot θ = 5
SOLUTION: Draw a right triangle and label one acute angle θ. Because cot θ = , label the side adjacent to θ as 5
= 5 or
and the opposite side 1.
By the Pythagorean Theorem, the length of the hypotenuse is
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or .
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4-1 Right Triangle Trigonometry
15. cot θ = 5
SOLUTION: Draw a right triangle and label one acute angle θ. Because cot θ = , label the side adjacent to θ as 5
= 5 or
and the opposite side 1.
By the Pythagorean Theorem, the length of the hypotenuse is
or .
17. sec θ = SOLUTION: Draw a right triangle and label one acute angle θ. Because sec θ = = , label the hypotenuse 9 and the side
opposite θ as 2.
By the Pythagorean Theorem, the length of the opposite side is
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or .
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4-1 Right Triangle Trigonometry
17. sec θ = SOLUTION: Draw a right triangle and label one acute angle θ. Because sec θ = = , label the hypotenuse 9 and the side
opposite θ as 2.
By the Pythagorean Theorem, the length of the opposite side is
or .
Find the value of x. Round to the nearest tenth.
19. SOLUTION: An acute angle measure and the length of the hypotenuse are given, so the sine function can be used to find the
length of the side opposite θ.
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SOLUTION: Page 4
An acute angle measure and the length of the hypotenuse are given, so the cosine function can be used to find the
length of the side adjacent to θ.
4-1 Right Triangle Trigonometry
21. SOLUTION: An acute angle measure and the length of the hypotenuse are given, so the cosine function can be used to find the
length of the side adjacent to θ.
23. SOLUTION: An acute angle measure and the length of the side opposite θ are given, so the sine function can be used to find the
length of the hypotenuse.
25. SOLUTION: An acute angle measure and the length of the side opposite θ are given, so the tangent function can be used to find
the length of the side adjacent to θ .
27. MOUNTAIN CLIMBING A team of climbers must determine the width of a ravine in order to set up equipment to cross it. If the climbers walk 25 feet along the ravine from their crossing point, and sight the crossing point on the
a 35º angle, how wide is the ravine?
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far side
of -the
ravine
be at
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4-1 Right Triangle Trigonometry
27. MOUNTAIN CLIMBING A team of climbers must determine the width of a ravine in order to set up equipment to cross it. If the climbers walk 25 feet along the ravine from their crossing point, and sight the crossing point on the
far side of the ravine to be at a 35º angle, how wide is the ravine?
SOLUTION: An acute angle measure and the adjacent side length are given, so the tangent function can be used to find the length
of the opposite side.
Therefore, the ravine is about 17.5 feet wide.
Find the measure of angle θ. Round to the nearest degree, if necessary.
31. SOLUTION: Because the lengths of the sides opposite and adjacent to θ are given, the tangent function can be used to find θ .
33. SOLUTION: Because the length of the hypotenuse and side opposite θ are given, the sine function can be used to find θ .
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4-1 Right Triangle Trigonometry
33. SOLUTION: Because the length of the hypotenuse and side opposite θ are given, the sine function can be used to find θ .
35. SOLUTION: Because the lengths of the sides opposite and adjacent to θ are given, the tangent function can be used to find θ .
37. SOLUTION: Because the length of the hypotenuse and side opposite θ are given, the sine function can be used to find θ .
39. PARASAILING Kayla decided to try parasailing. She was strapped into a parachute towed by a boat. An 800foot line connected her parachute to the boat, which was at a 32º angle of depression below her. How high above
the water was Kayla?
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SOLUTION: Page 7
The angle of elevation from the boat to the parachute is equivalent to the angle of depression from the parachute to
the boat because the two angles are alternate interior angles, as shown below.
4-1 Right Triangle Trigonometry
39. PARASAILING Kayla decided to try parasailing. She was strapped into a parachute towed by a boat. An 800foot line connected her parachute to the boat, which was at a 32º angle of depression below her. How high above
the water was Kayla?
SOLUTION: The angle of elevation from the boat to the parachute is equivalent to the angle of depression from the parachute to
the boat because the two angles are alternate interior angles, as shown below.
Because an acute angle and the hypotenuse are given, the sine function can be used to find x.
Therefore, Kayla was about 424 feet above the water.
41. ROLLER COASTER On a roller coaster, 375 feet of track ascend at a 55º angle of elevation to the top before
the first and highest drop.
a. Draw a diagram to represent the situation.
b. Determine the height of the roller coaster.
SOLUTION: a. Draw a diagram of a right triangle and label one acute angle 55º and the hypotenuse 375 feet.
b. Because an acute angle and the length of the hypotenuse are given, you can use the sine function to find the
length of the opposite side.
Therefore, the height of the roller coaster is about 307 feet.
43. BASKETBALL Both Derek and Sam are 5 feet 10 inches tall. Derek looks at a 10-foot basketball goal with an
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angle of elevation of 29°, and Sam looks at the goal with an angle of elevation of 43°. If Sam is directly in front of Derek, how far apart are the boys standing?
4-1 Right Triangle Trigonometry
Therefore, the height of the roller coaster is about 307 feet.
43. BASKETBALL Both Derek and Sam are 5 feet 10 inches tall. Derek looks at a 10-foot basketball goal with an
angle of elevation of 29°, and Sam looks at the goal with an angle of elevation of 43°. If Sam is directly in front of Derek, how far apart are the boys standing?
SOLUTION: Draw a diagram to model the situation. The vertical distance from the boys' heads to the rim is
10(12) – [5(12) + 10] or 50 inches. Label the horizontal distance between Sam and Derek as x and the horizontal
distance between Sam and the goal as y.
From the smaller right triangle, you can use the tangent function to find y.
From the larger right triangle, you can use the tangent function to find x.
Therefore, Derek and Sam are standing about 36.6 inches or 3.1 feet apart.
45. LIGHTHOUSE Two ships are spotted from the top of a 156-foot lighthouse. The first ship is at a 27º angle of
depression, and the second ship is directly behind the first at a 7º angle of depression.
a. Draw a diagram to represent the situation.
b. Determine the distance between the two ships.
SOLUTION: a.
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4-1 Right Triangle Trigonometry
Therefore, Derek and Sam are standing about 36.6 inches or 3.1 feet apart.
45. LIGHTHOUSE Two ships are spotted from the top of a 156-foot lighthouse. The first ship is at a 27º angle of
depression, and the second ship is directly behind the first at a 7º angle of depression.
a. Draw a diagram to represent the situation.
b. Determine the distance between the two ships.
SOLUTION: a.
b. From the smaller right triangle, you can use the tangent function to find y.
From the larger right triangle, you can use the tangent fuction to find x.
Therefore, the distance between the two ships is about 964 feet.
Solve each triangle. Round side measures to the nearest tenth and angle measures to the nearest
degree.
47. SOLUTION: Use trigonometric functions to find b and c.
Because the measures of two angles are given, B can be found by subtracting A from
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4-1 Right Triangle Trigonometry
Therefore, the distance between the two ships is about 964 feet.
Solve each triangle. Round side measures to the nearest tenth and angle measures to the nearest
degree.
47. SOLUTION: Use trigonometric functions to find b and c.
Because the measures of two angles are given, B can be found by subtracting A from
Therefore,
b
16.5, c
17.5.
49. SOLUTION: Use the Pythagorean Theorem to find r.
Use the tangent function to find P.
Because the measures of two angles are now known, you can find Q by subtracting P from
Therefore, P ≈ 43°, Q
47°, and r
34.0.
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SOLUTION: Use trigonometric functions to find j and k.
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Because the measures of two angles are now known, you can find Q by subtracting P from
4-1 Right Triangle Trigonometry
Therefore, P ≈ 43°, Q
47°, and r
34.0.
51. SOLUTION: Use trigonometric functions to find j and k.
Because the measures of two angles are given, K can be found by subtracting J from
Therefore,
j
18.0, k
6.2.
53. SOLUTION: Use trigonometric functions to find f and h.
Because the measures of two angles are given, H can be found by subtracting F from
Therefore,
f
19.6, h
17.1.
55. BASEBALL Michael’s seat at a game is 65 feet behind home plate. His line of vision is 10 feet above the field.
a. Draw a diagram to represent the situation.
b. What is the angle of depression to home plate?
SOLUTION: a.
b. Michael’s angle of depression to home plate is equivalent to the angle of elevation from home plate to where he is
sitting.
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Use the tangent function to find θ.
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Because the measures of two angles are given, H can be found by subtracting F from
4-1 Right Triangle Trigonometry
Therefore,
f
19.6, h
17.1.
55. BASEBALL Michael’s seat at a game is 65 feet behind home plate. His line of vision is 10 feet above the field.
a. Draw a diagram to represent the situation.
b. What is the angle of depression to home plate?
SOLUTION: a.
b. Michael’s angle of depression to home plate is equivalent to the angle of elevation from home plate to where he is
sitting.
Use the tangent function to find θ.
Therefore, the angle of depression to home plate is about
Find the exact value of each expression without using a calculator.
57. sin 60°
SOLUTION: Draw a diagram of a 30º-60º-90º triangle.
The length of the side opposite the 60° angle is
x and the length of the hypotenuse is 2x.
59. sec 30°
SOLUTION: Draw a diagram of a 30º-60º-90º triangle.
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The length of the hypotenuse is 2x and the length of the side adjacent to the 30º angle is
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x.
4-1 Right Triangle Trigonometry
59. sec 30°
SOLUTION: Draw a diagram of a 30º-60º-90º triangle.
The length of the hypotenuse is 2x and the length of the side adjacent to the 30º angle is
x.
61. tan 60°
SOLUTION: Draw a diagram of a 30º-60º-90º triangle.
The length of the side opposite the 60º is
x and the length of the adjacent side is x.
Without using a calculator, find the measure of the acute angle θ that satisfies the given equation.
63. tan θ = 1
SOLUTION: Because tan θ = 1 and tan θ = , it follows that
= 1. In the opposite an acute angle is 1 and the adjacent side length is also 1. So,
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Therefore, θ = 45°.
triangle below, the side length
= 1.
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4-1 Right Triangle Trigonometry
Without using a calculator, find the measure of the acute angle θ that satisfies the given equation.
63. tan θ = 1
SOLUTION: Because tan θ = 1 and tan θ = , it follows that
= 1. In the triangle below, the side length
= 1.
opposite an acute angle is 1 and the adjacent side length is also 1. So,
Therefore, θ = 45°.
65. cot θ =
SOLUTION: Because cot θ =
and cot θ = , it follows that
= . In the
triangle below, the side
length that is adjacent to the 60º angle is 1 and the length of the opposite side is
. So,
= or .
Therefore, θ = 60°.
67. csc θ = 2 SOLUTION: Because csc θ = 2 and csc θ = , it follows that
= 2 or . In the
hypotenuse is 2 and the side length that is opposite the 30º angle is 1. So,
triangle below, the
= or 2.
Therefore, θ = 30°.
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4-1 Right Triangle Trigonometry
Therefore, θ = 60°.
67. csc θ = 2 SOLUTION: Because csc θ = 2 and csc θ = , it follows that
= 2 or . In the
hypotenuse is 2 and the side length that is opposite the 30º angle is 1. So,
triangle below, the
= or 2.
Therefore, θ = 30°.
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