Expand the following: \begin{align} v_1 &= \cssId{Step1}{F_b2 = fN_2} \\[3px] &\cssId{Step2}{{} F_b2 = fF_G·cosα} \\[3px] &\cssId{Step3}{{} F_b2=\frac{v_0^2}{2gs_s}mg·cosα=\frac{v_0^2·cosα}{2s_s}}\\[3px] \end{align}