Using the image I gave you, you don't need to solve for x.
So tan is opposite/adjacent
sin: opposite/hypotenuse
cos: adjacent/hypotenuse
Take theta and do: adjacent/hypotenuse which is cosine
cos theta = adjacent/hypotenuse
cos theta = 1.5/9
inverse cos = 1.5/9 and the answer is: 80.4 degrees
