\(S = \left| {\left[ {\overrightarrow {AB} ,\overrightarrow {AD} } \right]} \right|\)         

\(S = \left| {\left[ {\overrightarrow {AB} ,\overrightarrow {AC} } \right]} \right|\)

\(S = \left[ {\overrightarrow {AB} ,\overrightarrow {AD} } \right]\)

\(S = \left| {\left[ {\overrightarrow {AC} ,\overrightarrow {AD} } \right]} \right|\)