Start with a sin graph (you could also use a cos graph)
change amplitude from 1 to 6 (the height of the wave is -2 to -14 a distance of 12 ....amplitude is 1/2 height)
6 sin x
shift the midline down from 0 to -8
6 sin x - 8
change period from 2pi to 2.5 pi 2pi / 2.5 pi = .8 Multiply the object of the sin fxn by .8
6 sin (.8x ) - 8
shift peak from the new peak 5pi/8 RIGHT to 6 pi/8 so subtract pi/8 from x
6 sin .8(x - pi/8) - 8 simplify a bit
6 sin (.8x - .1pi) - 8
Here is a graph :
https://www.desmos.com/calculator/lpxwuenxzi
