\[\boxed{\text{1002.\ }\text{еуроки}\text{-}\text{ответы}\text{\ }\text{на}\text{\ }\text{пятёрку}}\]
\[\textbf{а)}\ S = \frac{1}{2}\text{ah}\]
\[ha = 2S\]
\[h = \frac{2S}{a}.\]
\[\textbf{б)}\ \frac{S}{p} = 0,5m\]
\[p = \frac{S}{0,5m}\]
\[p = \frac{2S}{m}.\]
\[\textbf{в)}\ S = \frac{at^{2}}{2};\ \ t > 0\]
\[at^{2} = 2S\]
\[t^{2} = \frac{2S}{a}\]
\[t = \sqrt{\frac{2S}{a}}.\]