+9 $${\mathtt{a}} = {\frac{{\mathtt{1}}}{{\mathtt{2}}}}{\mathtt{\,\times\,}}{\mathtt{bh}} \Rightarrow {\mathtt{a}} = {\mathtt{0.5}}{\mathtt{\,\times\,}}\left(\underset{{\tiny{\text{Error: Unknown Identifier}}}}{{\mathtt{bh}}}\right)$$ find the area of this triangle
