The resultant of three vectors 1, 2 and 3 units whose directions are those of the sides of an equilateral triangle is

The vectors are shown in figureResolving the vectors along X, Y and Z axes, we haveRx =1+2cos120°+3cos240°Ry = 2 sin 120° + 3 sin 240°∴Rx=1−2×12−3×12=−32and Ry=2×(3/2)−3×(3/2)=−3/2Now tan⁡θ=RyRx=−(3/2)−(3/2)=13θ=tan−1⁡(1/3)= 1800-30∘ =1500