Answer
The size of television screen is $\text{32 inches}$.
Work Step by Step
Let $l$ = length of television and $w$ = width of television and $d$ = diagonal of television; all are in inches.
According to the Pythagoras theorem,
${{l}^{2}}+{{w}^{2}}={{d}^{2}}$
Here, $l=28\text{ and }w=15.7$
Therefore,
$\begin{align}
& {{d}^{2}}={{l}^{2}}+{{w}^{2}} \\
& ={{\left( 28 \right)}^{2}}+{{\left( 15.7 \right)}^{2}} \\
& =784+246.49 \\
& =1030.49
\end{align}$
Further simplify,
$\begin{align}
& d=\sqrt{1030.49} \\
& \approx 32
\end{align}$
Hence, the size of television screen is $\text{32 inches}$.
