The y-range for sin(x) is -1 to +1, so just scale it to suit.
yplot = 125 + sin(x)*25
Note: 125 = half-way between 100 and 150 = (100+150)/2
For the x-scale, it depends on you I suppose, but you could start with:
xplot = 125 + x*(25/360)
This will give x-values from -360 to +360, with x=0 at the center of the graph
If you want the sine to start at the lower left corner and go to the upper-right corner, then try:
xplot = 125 + x*(25/90)