(1)由图示：函数f(x)初相为第二象限角
T/2=3-(-1)=4==>T=8==>w=2π/T=π/4
∴f(x)=sin(π/4x+φ)
f(-1)=sin(-π/4+φ)=1==>-π/4+φ=π/2==>φ=3π/4
∴f(x)=sin(π/4x+3π/4)
(2)由图示：T/4=π/2-π/3=π/6==>T=2π/3==>w=2π/T=3,A=2
∴f(x)=2sin(3x+φ)
f(π/3)=2sin(π+φ)=2==>π+φ=π/2==>φ=-π/2
∴f(x)=2sin(3x-π/2)
(3)由图示：函数f(x)初相为第一象限角,A=2
3T/4=5π/6-π/12=3π/4==>T=π==>w=2π/T=2
∴f(x)=2sin(2x+φ)
f(π/12)=2sin(π/6+φ)=2==>π/6+φ=π/2==>φ=π/3
∴f(x)=2sin(2x+π/3)