Answer
$73^{\circ}F$
Work Step by Step
To find the average temperature in April, we need to substitute $x=4$ in the equation and solve:
$f(x)=12\sin[\frac{\pi}{6}(x-3.9)]+72$
$f(x)=12\sin[\frac{\pi}{6}(4-3.9)]+72$
$f(x)=12\sin[\frac{\pi}{6}(0.1)]+72$
$f(x)=12\sin[\frac{0.1\pi}{6}]+72$
$f(x)=0.628+72$
$f(x)=72.628\approx73$
Therefore, the average temperature in April is $73^{\circ}F$.
