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Book VI   Proposition 7
Let ABC, DEF be two triangles having one angle equal to one angle,
    the angle BAC to the angle EDF,
the sides about other angles ABC, DEF proportional, so that     as AB is to BC, so is DE to EF,
and, first,
    each of the remaining angles at C, F less than a right angle;

I say that the triangle ABC is equiangular with the triangle DEF,
    the angle ABC will be equal to the angle DEF,
and
    the ramaining angle, namely the angle at C, equal to the remaining angle, namely the angle at F.

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