Question

cos x = 0.39

(i) Find all the solutions of this equation for x in the interval (0, 2 pi]. Show every step of your solution. Use English to make it clear what you are doing.
In particular, I need for you to convince me that you have found all of the solutions requested. (Suggestion: The unit circle likely will help.)

(ii) Identify all of the solutions to the equation. You can and should make use of your work in part (i).

Answer 1

Do you know how to find one solution?

Answer 2

cos x = 0.39
Calculator gives cos x = 0.39 = cos 67.05 deg
Unit circle gives another arc that has the same cos value (0.39). That is the
arc x = -67.05 or (360 - 67.05) = 292.95 deg