clc
clear all
close all

 x1=[5 9 20]  
 plot(x1)  
 
 x1=0:0.1:2*pi;
 y1=sin(x1);  		%y1為x1的正弦函數
 plot(x1,y1);
 
 x=0:0.1:2*pi;
 plot(x,sin(x),x,cos(x),x,sin(3*x)) 
 
 x=0:0.1:2*pi;
 plot(x,sin(x),'r-.*')  	%用紅色，點劃線，數據點形用星號畫出曲線