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| 10 Theory slides |
| 9 Exercises - Grade E - A |
| Each lesson is meant to take 1-2 classroom sessions |
Here are a few recommended readings before getting started with this lesson.
Try your knowledge on these topics.
A submarine sailed underwater near a whale that was swimming 9 feet deeper than the submarine. A sonar on that submarine measured the angles of depression to the whale's mouth and tail to be 42∘ and 14∘, respectively.
How can the sailors use this information to measure the length of the whale?On the way to work, a man started wondering how tall his office building is. Suppose he is standing 10 meters from the building, looking up toward the rooftop at an approximate angle of 70∘. What is the height of the building?
Draw an angle at which the man is looking at the top of the building. Which trigonometric ratio can be used to find the building's height?
Start by drawing an angle at which the man is looking at the top of the building. Then identify a right triangle.
LHS⋅10=RHS⋅10
Rearrange equation
Use a calculator
Round to 1 decimal place(s)
Draw a right triangle so that the hypotenuse shows the expected path of the plane's descent. Analyze which side length is given to determine which trigonometric ratio should be used.
First, draw a right triangle, whose hypotenuse shows the expected path of descent of the plane and label the given distances on the diagram.
ba=b/2a/2
sin-1(LHS)=sin-1(RHS)
Use a calculator
Round to 1 decimal place(s)
In the previous two examples, the angles mentioned can be called the angle of elevation and angle of depression, respectively. To be able to refer to these angles, they should first be properly defined.
An angle of elevation is defined as an angle between the horizontal plane and oblique line from the observer's eye to some object above. Suppose someone is standing on the ground looking up toward the top of a tree.
An angle of depression is defined as an angle between the horizontal plane and oblique line from the observer's eye to some object below. Suppose someone is standing on a cliff looking down toward a ship in the ocean below.
A snowboarder is sliding down a ski hill that is 870 feet long. Its angle of depression is 12∘. What is the height of the ski hill?
Round the answer to the closest integer.Which trigonometric ratio describes the ratio between the height and the length of the ski hill in relation to the angle of depression?
It is given that the angle of depression of the ski hill is 12∘. That angle can be identified on the diagram as ∠θ. To determine the height of the hill, a line parallel to ℓ can be drawn at the bottom of the hill. By the Alternate Interior Angles Theorem, ∠θ and ∠1 are congruent angles.
It is also known that the length of the ski hill is 870 feet. Let h represent the height of the hill.
m∠1=12∘
LHS⋅870=RHS⋅870
Rearrange equation
Use a calculator
Round to nearest integer
Draw a right triangle formed by the ball and the goal post. Analyze the given side length and angle measures to determine which trigonometric ratio should be used.
Draw a right triangle based on the position of the ball and the goal post. In order to score, the ball should not rise higher than 10 feet. Therefore, to find the farthest position of Mark from the goal post, let one leg of the triangle be 10 feet long.
Calculate power
Add terms
Rearrange equation
LHS=RHS
Round to nearest integer
A family has a 7-foot tall sliding-glass door leading to the backyard. They want to buy an awning for the door that will be long enough to keep the Sun out when the Sun is at its highest point with an angle of elevation of 75∘.
Identify parallel lines and use the corresponding theorem to find the measure of an interior angle of a right triangle. Which trigonometric ratio can be used to find the length of the awning?
First, note that the concrete entrance way is parallel to the awning, so by the Alternate Interior Angles Theorem, ∠1 and the 75-degree angle are congruent angles.
LHS⋅7=RHS⋅7
Rearrange equation
Use a calculator
Round to 1 decimal place(s)
A mountaineer is planning to climb the highest mountain in the US, Denali, located in Alaska. When she reaches the peak, she wonders if she would be able to see the most eastern point of Russia, about 660 miles away from Denali.
Use the Pythagorean Theorem to find the distance from the top of the mountain to the horizon. The angle of depression can be found using one of the trigonometric ratios.
The exercise will be solved in two steps. First, the distance to the horizon will be calculated to find the answer to the given question. Then, the angle of depression will be determined.
Begin by representing the problem with a diagram. The horizon, or the farthest point the person could see, is the point where the line of sight of the mountaineer is tangent to the circle of the Earth. Let point C represent the center of the globe.
LHS−r2=RHS−r2
(a+b)2=a2+2ab+b2
Subtract term
LHS=RHS
Next, to find the angle of depression from the top of the mountain to the horizon, any of the trigonometric ratios can be used.
Throughout the lesson, different real-life problems have been solved using trigonometric ratios. Through the use of the learned methods, the challenge presented at the beginning can now be solved.
A submarine sailed underwater near a whale that was swimming 9 feet deeper than the submarine. A sonar on that submarine measured the angles of depression to the whale's mouth and tail to be 42∘ and 14∘, respectively.
How can the sailors use this information to measure the length of the whale?Use one of the trigonometric ratios to determine the horizontal distance from the submarine to the whale's nose and tale.
It is given that the angle of depression from the submarine to the whale's front is 42∘. Mark this information on the diagram and form a corresponding right triangle.
Using the tangent ratio, the horizontal distance from the submarine to the whale labeled as d1 can be found.
From the exercise, we know that the classmate is looking down at the harbor with an angle of depression of 20^(∘). We also know that the Statue of Liberty is 250 feet high. We can illustrate this with a diagram.
Notice that the angle of depression and one of the acute angles in the right triangle are complementary. This means the sum of their measures are 90^(∘). This information will help us determine the measure of the acute angle. m∠ θ+20^(∘) = 90^(∘) ⇓ m∠ θ = 70^(∘) The acute angle is 70^(∘). Let's add this to the diagram.
Now we can use the tangent ratio to determine d.
The distance from the base of the statue to the ship is approximately 687 feet.
We can illustrate this situation with a right triangle. We know that the slide is 7 feet high, and the angle of depression can, at most, be 40^(∘). We are looking for the minimum length of the slide, which we will label as a.
From the diagram, we see that the angle of depression and one of the acute angles in the right triangle are complementary. This means their measures sum to 90^(∘). With this information, we can determine the measure of the acute angle. m∠ θ+40^(∘) = 90^(∘) ⇓ m∠ θ = 50^(∘) The acute angle is 50^(∘). Let's add this to the diagram.
To determine the length of the slide, we can use the cosine ratio.
The minimum length of the slide is 10.9 feet.
Let's begin by drawing a diagram of the situation.
We know that the triangle is a right triangle, and we know the measurement of the adjacent side. We want to determine the building height — the length of the 53^(∘) angle's opposite side h. The tangent ratio makes it possible to solve the problem.
Together with Davontay, we have solved the height of the building to be about 73 feet.
Magdalena is standing on the top of a hill looking down at her house. The angle of depression she is looking with is 20∘.
The angle of depression is the angle between the horizontal plane and the line with which Magdalena is looking down. We know that this is 20^(∘). Let's draw this situation.
Similar to the angle of depression, the angle of elevation is the angle between the horizontal plane and the line with which someone looks up. Since both angles are measured with respect to the horizontal plane, they must be congruent.