Answer
$d=12.3$ m
Work Step by Step
We substitute $t=1.2$ in the equation and then solve for $d$:
$d=4\tan 2\pi t$
$d=4\tan 2\pi (1.2)$
$d=4\tan (2\pi \times1.2)$
$d=4\tan 2.4\pi$
Since $\tan 2.4\pi=3.07768$;
$d=4\tan 2.4\pi$
$d=4(3.07768)$
$d=12.311\approx12.3$
Therefore, for $t=1.2$ seconds, $d=12.3$ m.