Question

How do i do 13 A and 13 C

Answer 1

$\bf c^2=a^2+b^2\qquad \begin{cases} c=hypotenuse\\ a=adjacent\ side\\ b=opposite\ side\\ -------------\\ \textit{since they're equal}\\ \textit{let's call them "u"}\\ a=u\qquad since\qquad a=b\\ b=u\\ --------\\ c=850 \end{cases} \\ \quad \\ 850^2=u^2+u^2\implies 850^2=2u^2\implies \cfrac{850^2}{2}=u^2 \\ \quad \\ \sqrt{\cfrac{850^2}{2}}=u\implies \begin{cases} \sqrt{\cfrac{850^2}{2}}=a\\\\ \sqrt{\cfrac{850^2}{2}}=b \end{cases}$

now, for 13c
how much square feet will be covered? square feet means, Area,
namely, what is the area of that triangle?

well, now you know what sides "a" and "b" are,
area of a triangle is 1/2 b * h