Ta có:
\(\frac{S_{MAB}}{S_{MDC}}=\left(\frac{AB}{CD}\right)^2=\left(\frac{\frac{1}{3}CD}{CD}\right)^2=\frac{1}{9}\)
=> SMAB=\(\frac{1}{9}\)SMDC
<=> SMAB=\(\frac{1}{9}\)SMAB+\(\frac{1}{9}\)SABCD
<=> \(\frac{8}{9}S_{MAB}\)=\(\frac{16}{9}\)
=> SMAB=2 cm2