Tam giác \(ABC\) có \(\widehat A = 90^\circ \) .
Ta có: \(\sin \widehat B = \dfrac{{AC}}{{BC}};\sin \widehat C = \dfrac{{AB}}{{BC}}\)
Suy ra: \(\dfrac{{\sin \widehat B}}{{\sin \widehat C}} = \dfrac{{\dfrac{{AC}}{{BC}}}}{{\dfrac{{AB}}{{BC}}}} = \dfrac{{AC}}{{BC}}.\dfrac{{BC}}{{AB}} = \dfrac{{AC}}{{AB}}.\)
