Sinusoidal equations are trigonometric functions involving sine and cosine functions. Graphically, they look like wave patterns having amplitudes and periods. The general form of a sinusoidal equation is
y = A sin(Bx + C) + D
where
A = amplitude
B = frequency
C = shift on starting angle
D = shift of wave on the y-axis
From the given problem, A = 1 and D = 3. There is no value for C because there is no mention of any shift in angle. About the frequency, you can obtain this by getting the reciprocal of the period. Thus, B = 2/π. The complete equation is
y = sin(2x/π) + 3