Respuesta
For $30^\circ$-$60^\circ$-$90^\circ$: $x : x\sqrt{3} : 2x$ (opposite $30^\circ$ is $x$, opposite $60^\circ$ is $x\sqrt{3}$, hypotenuse is $2x$). For $45^\circ$-$45^\circ$-$90^\circ$: $x : x : x\sqrt{2}$.
Explicación
These ratios are also provided on the reference sheet at the beginning of each SAT math module, but memorizing them saves valuable test time.