i)The equilibrium is at y=3. c=3, the displacement of the curve from equilibrium. The amplitude a =6 and the perid from the gaph is pi so b=2pi/pi=2
ii)y=0 so 6sin(2x)+3=0 so sin(2x+3)=-0.5 so
2x=sin-1-0.5=-30
2x=180--30=210 x=105
2x=360+-30=330 so x=165
2x=540--30=570 so x=285
2x=720+-30=690 so x=345