We have to draw a voltage over time graph for the induced voltage in a coil for 2 whole turns.

$N = 10$
$B = 30mT$
$A = 100cm^2$

The coil is rotating at 20Hz

We have the formula:
$2πNBAfsin(2πfT)$

Every solution I get is positive and just rising with time. It should be a sine curve.

For example:

$U(\frac1{10}) = 2π \times 10 \times 0.03T \times 0.01m^2 \times 20Hz \times \sin(2π \times 20Hz \times 1/10s) = 0.0820$