Exercise 15 Page 865

We want to find the value of the given inverse trigonometric function. To do so we will use a calculator. Let's begin by making sure the calculator is in Degree mode. We do this by pushing $\boxed{\text{MODE}},$ selecting Degree instead of Radian in the third row, and pushing $\boxed{\text{ENTER}}.$

We are ready to go! Now we push $\boxed{2\text{ND}}$ followed by $\boxed{\text{COS}},$ type the given value, and push $\boxed{\text{ENTER}}.$ This will give us the value of $\text{Arccos }\frac{1}{2}$ in degrees.

The value of $\text{Arccos }\frac{1}{2}$ is $60^{\circ }.$