HiSET: Math : Problems involving right triangle trigonometry

Study concepts, example questions & explanations for HiSET: Math

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Example Questions

Example Question #1 : Sine

Evaluate  in terms of .

Possible Answers:

Correct answer:

Explanation:

Suppose we allow be the lengths of the opposite leg and adjacent leg and the hypotenuse, respectively, of the right triangle with an acute angle measuring .

The tangent of the angle is the ratio of the length of the opposite leg to that of the adjacent leg, so

We can set the lengths of the opposite and adjacent legs to and 5, respectively. The length of the hypotenuse can be determined using the Pythagorean Theorem:

The sine of the angle is equal to the ratio of the length opposite leg to that of the hypotenuse, so

.

Example Question #1 : Sine

Evaluate  in terms of .

Possible Answers:

Correct answer:

Explanation:

Suppose we allow be the lengths of the opposite leg and adjacent leg and the hypotenuse, respectively, of the right triangle with an acute angle measuring . The cosine is defined to be the ratio of the length of the adjacent side to that of the hypotenuse, so

We can set the lengths of the adjacent leg and the hypotenuse to and 3, respectively. By the Pythagorean Theorem, the length of the opposite leg is

The sine of the angle is equal to the ratio of the length of the opposite leg to that of the hypotenuse, so

.

Example Question #1 : Problems Involving Right Triangle Trigonometry

Evaluate  in terms of .

Possible Answers:

Correct answer:

Explanation:

Suppose we allow be the lengths of the opposite leg and adjacent leg and the hypotenuse, respectively, of the right triangle with an acute angle measuring .

The tangent of the angle is the ratio of the length of the opposite leg to that of the adjacent leg, so

We can set the lengths of the opposite and adjacent legs to and 5, respectively. The length of the hypotenuse can be determined using the Pythagorean Theorem:

The cosine of the angle is equal to the ratio of the length of the adjacent leg to that of the hypotenuse, so

.

Example Question #1 : Problems Involving Right Triangle Trigonometry

Possible Answers:

None of the other choices gives the correct response.

Correct answer:

None of the other choices gives the correct response.

Explanation:

An identity of trigonometry is

for any value of .

Since , it immediately follows that .

This response is not among the given choices.

Example Question #1 : Problems Involving Right Triangle Trigonometry

Right

Refer to the triangle in the above diagram. Which of the following expressions correctly gives its area?

Possible Answers:

None of the other choices gives the correct response.

Correct answer:

Explanation:

The area of a right triangle is half the product of the lengths of its legs, which here are  and  - that is, 

We are given that  is the leg opposite the angle  and  is its adjacent leg, we can find  using the tangent ratio:

Setting  and , we get

Solve for  by multiplying both sides by 12:

Now, set  and  in the area formula:

,

the correct choice.

 

Example Question #1 : Problems Involving Right Triangle Trigonometry

Right

Refer to the triangle in the above diagram. Which of the following expressions correctly gives its area?

Possible Answers:

None of the other choices gives the correct response.

Correct answer:

Explanation:

The area of a right triangle is half the product of the lengths of its legs, which here are  and  - that is, 

We are given that  is the leg opposite the angle  and  is its adjacent leg, we can find  using the tangent ratio:

Setting  and , we get

Solve for  by first, finding the reciprocal of both sides:

Now, multiply both sides by 8:

Now, set  and  in the area formula:

,

the correct choice.

 

Example Question #1 : Problems Involving Right Triangle Trigonometry

Evaluate  in terms of .

Possible Answers:

Correct answer:

Explanation:

Suppose we allow be the lengths of the opposite leg and adjacent leg and the hypotenuse, respectively, of the right triangle with an acute angle measuring . The cosine is defined to be the ratio of the length of the adjacent side to that of the hypotenuse, so

We can set the lengths of the adjacent leg and the hypotenuse to and 3, respectively. By the Pythagorean Theorem, the length of the opposite leg is

The tangent of the angle is the ratio of the length of the opposite leg to that of the adjacent leg, so

.

Example Question #1 : Problems Involving Right Triangle Trigonometry

Possible Answers:

Correct answer:

Explanation:

The sine of an angle is defined to be the ratio of the length of the opposite leg of a right triangle to the length of its hypotenuse. Therefore, we can set . By the Pythagorean Theorem:
 the adjacent leg of the triangle has measure

The tangent of the angle is the ratio of the length of the opposite leg to that of the adjacent leg, which is

,

the correct response.

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