Use a trigonometric solution to find the magnitude of the resultant of the following coplanar forces

To find the magnitude of the resultant of  60N at 90 degrees, 80N at 120 degrees and 100 N at 270 degree, you will just minus 180 degrees to 180 degrees since the remaining angle is the resultant velocity of the unmeasured side of the angle. Since there is a given of 30 degrees, then 180 degrees-30 degree = 150 degrees. Th magnitude is Ncos150 where N=squareroot of A^2+B^2 and the answer is 128.06
SO magnitude= 128.06cos150
=110.91
or 111

Dis the solution here