Evaluate the definite integral.

${\displaystyle \underset{0}{\overset{\frac{}{3}}{}}}si{n}^2(x)co{s}^3(x)dx$

$(Express$ numbers $in$ exact form. Use symbolic notation and fractions where needed.$)$

${\displaystyle \underset{0}{\overset{\frac{}{3}}{}}}si{n}^2(x)co{s}^3(x)dx=$