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function b7
clc
t=linspace(0,2*pi,50);
[x,y]=meshgrid(sqrt(3)*cos(t)-1,sqrt(3)*sin(t));
z=x.^2+y.^2;
set(surf(x,y,z),'facecolor','b','edgecolor','non','facealpha',.1)
hold on
z=2-2.*x;
set(surf(x,y,z),'facecolor','g','edgecolor','non','facealpha',.1)
% ve duong giao tuyen
t=linspace(0,2*pi,50);
x=sqrt(3)*cos(t)-1;y=sqrt(3)*sin(t);z=x.^2+y.^2;
plot3(x,y,z,'color','r')
%tinh tich phan mat
syms x y z real
P=3*x-+y^2;
Q=3*y-z^2;
R=3*z-x^2;
f=z+2*x-2;
n=[diff(f,'x') diff(f,'y') diff(f,'z')];
n=n/sqrt(diff(f,'x')^2 + diff(f,'y')^2 + diff(f,'z')^2); % tinh vector don vi cua vector phap
%phuong phap tinh la phuong phap stokes
p=(diff(R,'y')-diff(Q,'z'))*n(1,1);
q=(diff(P,'z')-diff(R,'x'))*n(1,2);
r=(diff(Q,'x')-diff(P,'y'))*n(1,3);
z=2-2*x;
% chuyen ve tich phan mat loai 1
f=(eval(p)+eval(q)+eval(r))*sqrt(1+diff(z,'x')^2+diff(z,'y')^2);
%tinh tich phan
syms r phi real
x=r*cos(phi);y=r*sin(phi); % chuyen sang phuong phap truc toa do
f=eval(f);
S=int(int(f*r,'r',0,sqrt(3)),'phi',0,2*pi); %tinh tich phan
S=double(S);
disp(['Tich phan can tinh la: I= ' num2str(S)])
% ve vector phap tai M0
disp('nhap diem M0 thuoc mat 2*x+z=2 va z >= x^2+y^2 ')
disp('vidu M(0,-1,2), thi ta nhap: 0,-1,2')
m=input('M0= ','s');
m=str2num(m);
x=m(1,1);y=m(1,2);z=m(1,3);
n=eval(n);% the toa do diem vao vector
title(['mat z=y^2 nam trong hinh tru x^2+y^2=1 ' 'Va phap vector tai diem M0(' num2str(x) ',' num2str(y) ',' num2str(z) ')']) % tao tieu de
%bat dau ve vector phap
t=linspace(0,1,20);
x=n(1,1)*t+x;
y=n(1,2)*t+y;
z=n(1,3)*t+z;
plot3(x,y,z,'color','r')
hold off
rotate3d on
% OK men :))
end
Tìm hiểu thêm về rainbowsmile
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