Question 32568
Equation you want is y=Asin(BX+C)+D
amplitude = A = (7000-2000)/2=2500
period = 6 mths = (2pi/B); so B=pi/6
Shift = -C/B=-C/[pi/6]; shift is 6 mths to the left; 
So -C/[pi/6]=+6 and C=-pi
Translation is +4500; so D=4500
Equation is y=2500sin[(pi/6)t-pi]+4500
Cheers,
Stan H.