y=4cos(6(x-π/9))-1=4cos(6x-2π/3)-1
五点作图法
6x-2π/3 0 π/2 π 3π/2 2π
x 4π/36 7π/36 10π/36 13π/36 16π/36
y 3 -1 -5 -1 3
描点 (4π/36,3) (7π/36,-1)(10π/36,-5)(13π/36,-1)(16π/36,3)
y=4cos(6(x-π/9))-1=4cos(6x-2π/3)-1
五点作图法
6x-2π/3 0 π/2 π 3π/2 2π
x 4π/36 7π/36 10π/36 13π/36 16π/36
y 3 -1 -5 -1 3
描点 (4π/36,3) (7π/36,-1)(10π/36,-5)(13π/36,-1)(16π/36,3)