
William W. answered 11/16/20
Experienced Tutor and Retired Engineer
The distance between the midline intersection and the first maximum for a sine wave is 1/4 of the period. In this case that is 4(4.1 - (-3.5)) = 4•7.6 = 30.4.
As an FYI, the amplitude is the "y" difference between the midline and the maximum so 0.7 - (-0.8) = 1.5 so the function would be:
y = 1.5sin(5π/76(x + 3.5)) - 0.8 with a curve like this: