Answer
$V\approx 4.186\approx 4.2~in^3$
Work Step by Step
We know that the volume of a cone (radius $r$, height $h$) is given by:
$\displaystyle V=\frac{1}{3}\pi r^2 h$
We plug in our values ($r=diameter/2=2/2=1~in$, $h=4~in$) to find the volume:
$\displaystyle V=\frac{1}{3}\pi 1^2 4$
$\displaystyle V=\frac{4\pi}{3}$
$V\approx 4.186\approx 4.2~in^3$
