Gōngchéngshī / yòng / ōushì jǐhé / de / fāngfǎ / zhèngmíng / le / zhège / túxíng / de / duìchènxìng工程师用欧式几何的方法证明了这个图形的对称性。The engineer used a method from Euclidean geometry to prove the symmetry of this figure.