# HiSET: Math : Cosine

## Example Questions

### Example Question #3 : Problems Involving Right Triangle Trigonometry

Evaluate  in terms of .

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 #4 : Problems Involving Right Triangle Trigonometry

None of the other choices gives the correct response.

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.