a + b + c = 180° m[A] + m[B] + m[C] = 180°
a' + b' + c' = 360° m(DAF)+m(ABE)+m(BCF)=360°
m(ACD)=a+b m(DAC) = m(A') = b + c m(DBE) = m(B') = a + c m(ECF) = m(C') = a + b
lABl=lACl Û m[B]=m[C]
|AB| = |BC| = |AC| m[A] + m[B] + m[C]= 60°