matlab中如何以一个点为圆心画圆

用程序作图：R1=10;R2=6.6;R3=2; %定义半径phi=0:pi/20:2*pi;x1=R1*cos(phi);y1=R1*sin(phi);x2=R2*cos(phi);y2=R2*sin(phi);figureplot(x1,y1,x2,y2) %画内外圆axis([-R1-2,R1+2,-R1-2,R1+2])axis equalhold onplot(0,0,'.') %画圆心bx=R1*cos(pi/4);by=R1*sin(pi/4);ex=0;ey=R1;ax=R1*cos(3*pi/4);ay=R1*sin(3*pi/4);plot([0,ax],[0,ay]) %画OA线plot([0,bx],[0,by]) %画OB线plot([0,ex],[0,ey]) %画OE线plot([-R1-1,R1+1],[R2,R2],'--') %画切线plot([ax,0,bx],[ay,R2,by])text(0.6,0,'O','fontsize',16) %标出O点text(bx+0.2,by+0.5,'B','fontsize',16) %标出B点text(ex,ey+1,'E','fontsize',16) %标出E点text(ax-1,ay+0.5,'A','fontsize',16) %标出A点text(-sqrt(R1^2-R2^2)-2,R2-0.8,'D','fontsize',16)%标D点text(sqrt(R1^2-R2^2)+1,R2-0.8,'C','fontsize',16) %标C点phi2=pi/4:pi/40:3*pi/4;x3=R3*cos(phi2);y3=R3*sin(phi2);plot(x3,y3) %画圆弧title('MATLAB作图','fontsize',16) %标题 运行结果如下：</p