met de rekenmachine
$
\eqalign{
& \tan \angle C = \frac{{AB}}
{{BC}} \cr
& \tan \angle C = \frac{4}
{3} \cr
& \angle C \approx 53^\circ \cr}
$
$
\eqalign{
& \tan \angle C = \frac{{AB}}
{{BC}} \cr
& \tan 53^\circ = \frac{4}
{x} \cr
& x = \frac{4}
{{\tan 53^\circ }} \approx 3 \cr}
$
$
\eqalign{
& \tan \angle C = \frac{{AB}}
{{BC}} \cr
& \tan 53^\circ = \frac{x}
{3} \cr
& x = 3 \cdot \tan 53^\circ \approx 4 \cr}
$
