Calculus Tip: For integrals of the form $\int \sin^m x \cos^n x dx$, if $(m+n)$ is a negative even integer (here, $-4/3 - 2/3 = -2$), dividing the numerator and denominator by $\cos^{-(m+n)}x$ (here, $\cos^2 x$) is the standard technique to convert the expression into terms of $\tan x$ and $\sec^2 x$.