My comments are with respect to posts # 1, 2, and 3, refering specifically to the cos x = -5/11, and the op's question about how could x be 117 degrees as well as 243 degrees. The way I arrive at the 243 is by adding 63 to 180 (because I know that 180 - 117 = 63) or by subtracting 117 from 360. You get to the same angle (243) either way. I'm no math whiz, but THIS much I know! Given that, and the context of posts 1, 2, and 3, I'm not sure what 360 - (180 - 117) is supposed represent. If I were a student in your class, I'd be calling you out on that one