find the value of x cos(3x)= -0.419 for 0<x<270 I do arc cos -0.419 which equals 114.77 and then to find the second angle in the 3rd quadrant why do I need to minus 360 to get the degree in the 3rd quadrant? why not add 90 to 114.77 to make it in the 3rd quadrant? someone please explain this