Answer
The triangle with vertices (7,2,0),(7.5,5,0),(5,5,0)
Work Step by Step
$P D=\left[\begin{array}{cccc}1 & 0 & 0 & 0 \\ 0 & 1 & 0 & 0 \\ 0 & 0 & 0 & 0 \\ 0 & 0 & -\frac{1}{10} & 1\end{array}\right]\left[\begin{array}{ccc}4.2 & 6 & 2 \\ 1.2 & 4 & 2 \\ 4 & 2 & 6 \\ 1 & 1 & 1\end{array}\right]=\left[\begin{array}{ccc}4.2 & 6 & 2 \\ 1.2 & 4 & 2 \\ 0 & 0 & 0 \\ 0.6 & 0.8 & 0.4\end{array}\right]$
Make $\mathrm{P}$ is the projection matrix and
Make $\mathrm{D}$ be the Data matrix for S using homogeneous coordinates. The data matrix for the image $\mathrm{S}$ is PD.
\[
\left[\begin{array}{ccc}
7 & 7.5 & 5 \\
2 & 5 & 5 \\
0 & 0 & 0
\end{array}\right]
\]
To get coordinates divide top three entries in each
column by the corresponding entry in the fourth column.
\[
(7,2,0),(7.5,5,0),(5,5,0)
\]
