If two triangle $(\triangle BAC, \triangle EDF)$ have two sides $(BA, AC)$ of one equal respectively to two sides
$(ED, DF)$ of the other, and have also the angles $(\angle A, \angle D)$ included by those sides equal, the triangles shall be equal in every respect – that is, their bases or third sides $(BC, EF)$ shall be equal, and the angles $(\angle B, \angle C)$ at the base of one shall be respectively equal to the angles $(\angle E, \angle F)$ at the base of the other; namely, those shall be equal to which the equal sides are opposite.