Using calculator, we find:

(1) `cos(pi/6) = cos 30^"o" =\ 0.8660254`

0.86601π/6Open image in a new page

30° - 60° triangle showing `cos(pi/6) = 0.8660254`.

(2) `sec 4.5 = -4.7439275`

4.5Open image in a new page

The angle 4.5 radians.

(3) `sec 4.5^"o" = 1.0030922`

4.5°Open image in a new page

The angle 4.5 degrees.

Notice the difference between these last two. Without the degree sign, 4.5 means "4.5 radians". It is important to set your calculator properly before starting these problems.