EDEXCEL GCE C3 Trigonometry help

Hi,I would appreciate if someone could answer my inquiry. When answering trigonometric questions in C3 such as,

"Hence solve, for 0 < x < 360°, the equationcos 2x + sin x = 1"

are the following equations correct to use for finding values for x
sinx = x + 360n
=(180 - x) + 360n
When I look at my textbooks and past papers this method is nowhere to be seen but i still get the correct answers for the questions