AB song song với CD

\( \Rightarrow {S_{BAD}} = {S_{ABC}} \Rightarrow {S_{BAD}} - {S_{OAB}} = {S_{ABC}} - {S_{OAB}} \Rightarrow {S_{OAD}} = {S_{OBC}} = 10c{m^2}\)

\(\frac = \frac{{{S_{OAB}}}}{{{S_{OAD}}}} = \frac{6} = \frac{3}{5}\)

\(\frac{{{S_{OBC}}}}{{{S_{ODC}}}} = \frac = \frac{3}{5}\)

\( \Rightarrow {S_{ODC}} = \frac{5}{3}{S_{OBC}} = \frac{5}{3}.10 = \frac{3}\left( {c{m^2}} \right)\)

\({S_{ABCD}} = {S_{OAB}} + {S_{OAD}} + {S_{OBC}} + {S_{ODC}} = 6 + 10 + 10 + \frac{3} = \frac{3}\left( {c{m^2}} \right)\).