绘制命令如下：
x2=-1:0.01:1;
y2=acos(x2);
x3=-pi:0.01:pi;
y3=cos(x3);
plot(x2,y2,x3,y3);
grid on;
绘制命令如下：
x2=-1:0.01:1;
y2=acos(x2);
x3=-pi:0.01:pi;
y3=cos(x3);
plot(x2,y2,x3,y3);
grid on;
