y=sin(2x)
x0π/4π/2 3π/4 π
y010 -1 0
y=2sinx
x0π/2 π 3π/2 2π
y0 20-20
y=sina(2x+π/4)
x-π/8 π/8 3π/8 5π/87π/8
y01 0 -1 0
注：我不知道那个y=sina(2x+π/4)里的a什么意思,当作y=sin (2x+π/4)的来写