In the cube \(ABCDEFGH\) find the
angle between the lines \(S_{AE}S_{HC}\)
and \(S_{HC}S_{BF}\),
where \(S_{AE}\),
\(S_{HC}\) and
\(S_{BF}\) are the centers
of the segments \(AE\),
\(HC\) and
\(BF\),
respectively.
The lengths of a side, face diagonal and solid diagonal through the vertex
\(A\) in a rectangular
box \(ABCDEFGH\)
are \(|AB| = 6\, \mathrm{cm}\),
\(|AC| = 10\, \mathrm{cm}\),
\(|AG| = 15\, \mathrm{cm}\). Find
the surface area.
Consider a triangle \(ABC\) with
sides of the lengths \(3\, \mathrm{cm}\),
\(4\, \mathrm{cm}\) and
\(4\, \mathrm{cm}\). Identify the type
of the triangle \(ABC\).