http://prntscr.com/mblu9p
No....sorry. 3 is the amplitude of the modulated wave. Normal midline for a cos wave is y = 0 . This wave is SHIFTED DOWNWARD by 2.5 so the midline woudl be at y = -2.5 .
You can check your own graphs with this calculator
https://www.desmos.com/calculator
+37158 
