1)
a)
A(ABCD) = AB·BC = 12·18 = 216 cm²
b)
A(RMD) = A(ABCD) - A(DAR) - A(RBM) - A(MCD)
A(DAR) = DA·AR/2 = 18·6/2 = 54 cm²
A(RBM) = RB·BM/2 = 6·6/2 = 18 cm²
A(MCD) = MC·CD/2 = 12·12/2 = 72 cm²
A(RMD) = 216 - 54 - 18 - 72 = 72 cm²
c)
ND = √CN² + CD² = √36 + 144 = √180 = 6√5 cm
NR = √NB² + BR² = √144 + 36 = √180 = 6√5 cm
DR = √AD² + AR² = √144 + 36 = √180 = 6√5 cm
ND = NR = DR =>ΔRND = echilateral
