Answer
$$\int_{0}^{\pi / 3} \sec ^{3 / 2} x \tan x d x =\frac{4\sqrt{2}}{3}-\frac{2}{3}$$
Work Step by Step
$$
\int_{0}^{\pi / 3} \sec ^{3 / 2} x \tan x d x
$$
Since
\begin{align*}
\int_{0}^{\pi / 3} \sec ^{3 / 2} x \tan x d x&=\int_{0}^{\pi / 3} \sec ^{1 / 2}x(\sec x \tan x )d x\\
&=\frac{2}{3}\sec^{3/2}x\bigg|\int_{0}^{\pi / 3} \\
&=\frac{4\sqrt{2}}{3}-\frac{2}{3}
\end{align*}