Cost of Capital:

${}_i=\frac{{}_{i,M}{}_i}{{}_m}=\frac{{}_{i,M}{}_i{}_m}{{}_m^2}=\frac{\text{C}\text{o}\text{v}(r_i,r_M)}{{}_m^2}$

$r_i=r_f+{}_i(E[R_{mkt}]-r_f)$

$r_{\text{w}\text{a}\text{c}\text{e}}=\frac{E}{E+D}{r}_E+\frac{D}{E+D}{r}_D(1-r_c)$

How are these formulas used? Please provide examples.