### Home > INT3 > Chapter 2 > Lesson 2.1.1 > Problem 2-9

2-9.

For each diagram below, write and solve an equation to calculate the value of the variable. If you need help, refer to the Math Notes box in this lesson. State your answer to part (d) in both approximate decimal form and radical form.

Use your calculator to compute

. Does your answer seem reasonable? If not, verify that your calculator is in degree mode.

Follow the steps in part (a).

How can you "undo" cosine?

An angle is not marked, just three sides. What formula uses three sides of a right triangle?

Pythagorean Theorem