diff --git a/hw3_10_4.m b/hw3_10_4.m
new file mode 100644
index 0000000..faf42f2
--- /dev/null
+++ b/hw3_10_4.m
@@ -0,0 +1,20 @@
+%a------------
+
+teta = pi/3;
+F = [-cos(teta) sin(teta); sin(teta) cos(teta)];
+J = [cos(teta) sin(teta); -sin(teta) cos(teta)];
+v = [2;1];
+fRes = F*v
+jRes = J*v    
+
+atan2(fRes(2),fRes(1))
+atan2(v(2),v(1))
+figure;
+plotv(F*v,'-');
+hold
+plotv(v,'-');
+plotv(J*v,'-');
+ % J rotates plane by the angle teta in the clockwise direction
+ % F takes the symmetric of v according to y axis, then rotates plane by teta
+ % degree in the counter clockwise direction.
+%-------------
\ No newline at end of file
diff --git a/hw3_11_3.m b/hw3_11_3.m
new file mode 100644
index 0000000..d52ff50
--- /dev/null
+++ b/hw3_11_3.m
@@ -0,0 +1,96 @@
+function hw3_11_3
+    m = 50;
+    n = 12;
+
+    t = linspace(0,1,m);
+
+    tmp = fliplr(vander(t));
+    A = tmp(:,1:n);
+    b = cos(4*t);
+
+    %a-------------------
+    x1 = (A'*A) \ (A'*b');
+    %--------------------
+
+    %b-------------------
+    [Q, R] = mgs(A);
+    v = Q' * b';
+    x2 = R\v; 
+    %--------------------
+
+    %c-------------------
+
+    [W, R] = house(A);
+    Q = zeros(m, m);
+    for i = 1:m
+        e = zeros(m,1);
+        e(i) = 1;
+        Q(:,i) = formQx(W,e);
+    end
+
+    vec = b';
+    for i = 1:n
+        vec(i:m)=vec(i:m)-2*W(i:m,i)*((W(i:m,i))'*vec(i:m));
+    end
+    x3 = R\vec;
+
+    %--------------------
+
+    %d-------------------
+    [Q, R] = qr(A);
+    v = Q' * b';
+    x4 = R\v; 
+    %--------------------
+
+    %e-------------------
+    x5 = A\b';
+    %--------------------
+
+    %f-------------------
+    [U,S,V] = svd(A);
+    x6 = V*(S\(U'*b'));
+    %--------------------
+
+    [x1 x2 x3 x4 x5 x6]   
+    
+   function [Q, R] = mgs(A)
+       n = size(A,2);
+       V = A;
+       Q = zeros(size(A,1), size(A,2));
+       R = zeros(n,n);
+
+       for k = 1:n
+           R(k,k) = norm(V(:,k));
+           Q(:,k) = V(:,k)/R(k,k);
+           for j = k+1:n
+               R(k,j) = Q(:,k)' * V(:,j);
+               V(:,j) = V(:,j) - R(k,j) * Q(:,k);
+           end
+       end
+   end
+    function [W,R]=house(A) 
+        m=size(A,1);
+        n=size(A,2);
+        W=zeros(m,n);
+        for k=1:n
+            x=A(k:m,k);
+            e1=eye(m-k+1,1);
+            if (x(1)==0) coef=1;
+            else coef=sign(x(1));
+            end;
+            W(k:m,k)=coef*norm(x,2)*e1+x;
+            W(k:m,k)=W(k:m,k)/norm(W(k:m,k),2);
+            A(k:m,k:n)=A(k:m,k:n)-2*W(k:m,k)*((W(k:m,k))'*A(k:m,k:n));
+        end;
+        R=triu(A,0);
+    end
+
+    function a=formQx(W,vect)
+        m=size(W,1);
+        n=size(W,2);
+        for k=n:-1:1
+            vect(k:m)=vect(k:m)-2*W(k:m,k)*((W(k:m,k))'*vect(k:m));
+        end;
+        a=vect;
+    end
+end
\ No newline at end of file
diff --git a/hw3_9_3.m b/hw3_9_3.m
new file mode 100644
index 0000000..80bd52c
--- /dev/null
+++ b/hw3_9_3.m
@@ -0,0 +1,36 @@
+A = zeros(15,40);
+%a-----------
+vertical = [2 2; 2 3; 2 6; 2 7; 3 10; 3 11; 4 18; 4 19; 5 26; 5 27; 6 34; 6 35; 6 38; 6 39];
+horizontal = [5 2; 6 2;3 10;4 10; 6 10; 7 10;9 10;10 10;10 18; 11 18;11 26;12 26;6 34; 7 34; 12 34; 13 34];
+
+
+for i = 1:length(vertical)
+    A(vertical(i,1):vertical(i,1)+7,vertical(i,2)) = 1;
+end
+
+for i = 1:length(horizontal)
+    A(horizontal(i,1),horizontal(i,2):horizontal(i,2)+5) = 1;
+end
+%spy(A);
+%a------------
+
+%b------------
+S = svd(A)
+figure
+plot(S)
+title('plot');
+figure
+semilogy(S)
+title('semilogy');
+rank(A)
+%b------------
+
+%c------------
+[U, S, V] = svd(A);
+figure
+for i = 1:rank(A)
+    B = U(:,1:i) * S(1:i, 1:i) * V(:,1:i)'
+    pcolor(B)
+    colormap(gray)
+end
+%c------------
\ No newline at end of file