定理设面ABC三边为a，b，c，周界中点三角形相应边为a’，b’，c’，则证明设D、E、F分别为西ABC的边BC、CA、AB边上的周界中点．从E、F作EM上BC于M，FN上BC于N，NV（如图3）但BF—CE一户一a，因此上式即为a’＞a一（p—a）（cosB＋cosC）．再由关于y，C’的类似不等式，三式相 Theorem sets the three edges of surface ABC to a, b, and c, and the corresponding edges of the midpoint of the perimeter are a’, b’, and c’. It is proved that D, E, and F are the edges of the western ABC’s edges BC, CA, and AB, respectively. Perimeter midpoint. From E, F for EM on BC on M, on FN for BC on N, NV (as in Figure 3) but BF-CE for one account on a, so the above equation is a’> a (p-a) (cosB + cosC) . Then by the similar inequality about y, C’, the triadic phase