Show that, for a boundary layer with $=0,$ the streamwise variation of the skin$-$friction

coefficient is given by

$R{e}_x=\frac{1}{{}^3}({}^2-4+6)e^{(-Bx)}$

where $=x\sqrt[\phantom{2}]{\frac{2}{f_F}}.$

If $=0\mathrm{.}4,B=5\mathrm{.}5,$ and $\frac{c_f}{2}=7\mathrm{.}15{10}^{-4},$ find the value of $R{e}_x$ using this formula.

Use the calculated value of $R{e}_x$ to calculate $\frac{c_f}{2}$ from White's formula:

$\frac{c_f}{2}=\frac{0\mathrm{.}2275}{l{n}^2(0\mathrm{.}068e_x)}$