Solució: \begin{align} ∑ F = ma = 0 &= \cssId{Step1}{F_C·cosφ + F_B·cosφ} \\[3px] &\cssId{Step2}{(F_C + F_B)·cosφ = 0} \\[3px] &\cssId{Step3}{F_C + F_B = 0} \\[3px] &\cssId{Step4}{F_C = -F_B} \\[3px] \end{align}