Two forces are given at 15 degree and the equilibrant is required between them
The formula to find the equilibrant is given by
[tex]F = \sqrt{F_1^2 + F_2^2 + 2F_1F_2 cos\theta}
[tex]F = \sqrt{1210^2 + 1540^2 + 2*1210*1540*cos15]
[tex]F = 2726.8 lb[/tex]
So the magnitude of equilibrant is 2726.8 lb
now in order to find the angle with respect to 1210 lb we can say
[tex]\phi = tan^{-1}\frac{1540sin\theta}{1210 + 1540cos\theta}[/tex]
[tex]\phi = tan^{-1}0.147[/tex]
[tex]\phi = 8.4 degree[/tex]