initial commit / add all books

38 files changed, 408 insertions, 0 deletions

diff --git a/40/CH8/EX8.1/Exa_8_1.sce b/40/CH8/EX8.1/Exa_8_1.sce
new file mode 100755
index 000000000..000b8b907
--- /dev/null
+++ b/40/CH8/EX8.1/Exa_8_1.sce
@@ -0,0 +1,6 @@
+//DFT from defining relation

+//N-point DFT

+x=[1 2 1 0];

+XDFT=dft(x,-1);

+disp(XDFT,'The DFT of x[n] is');

+//DFT of periodic signal x with period N=4
\ No newline at end of file
diff --git a/40/CH8/EX8.10/Exa_8_10.sce b/40/CH8/EX8.10/Exa_8_10.sce
new file mode 100755
index 000000000..d9676ae26
--- /dev/null
+++ b/40/CH8/EX8.10/Exa_8_10.sce
@@ -0,0 +1,9 @@
+//DFS of sampled periodic signals

+xn=[0 ones(2:16) 0 -ones(18:32)];

+XDFS=0.032*dft(xn,-1);

+for i=1:length(XDFS)

+    if (abs(XDFS(i))<0.000001) then

+        XDFS(i)=0;

+    end

+end

+disp(XDFS,'The DFS of x[n] is');
\ No newline at end of file
diff --git a/40/CH8/EX8.11/Exa_8_11.sce b/40/CH8/EX8.11/Exa_8_11.sce
new file mode 100755
index 000000000..5b086398e
--- /dev/null
+++ b/40/CH8/EX8.11/Exa_8_11.sce
@@ -0,0 +1,27 @@
+//Effects of leakage

+n1=0:0.005:0.1;

+n2=0:0.005:0.125;

+n3=0:0.005:1.125;

+xt1=(2*cos(20*%pi*n1')+5*cos(100*%pi*n1'));

+xt2=(2*cos(20*%pi*n2')+5*cos(100*%pi*n2'));

+xt3=(2*cos(20*%pi*n3')+5*cos(100*%pi*n3'));

+XDFS1=abs(dft(xt1,-1))/20;

+XDFS2=abs(dft(xt2,-1))/25;

+XDFS3=abs(dft(xt3,-1))/225;

+f1=0:5:100;

+f2=0:4:100;

+f3=0:100/225:100;

+a=gca();

+a.x_location="origin";

+plot2d3('gnn',f1,XDFS1);

+xlabel('analog frequency');

+ylabel('Magnitude');

+xset('window',1);

+subplot(211);

+plot2d3('gnn',f2,XDFS2);

+xlabel('analog frequency');

+ylabel('Magnitude');

+subplot(212);

+plot2d3('gnn',f3,XDFS3);

+xlabel('analog frequency');

+ylabel('Magnitude');
\ No newline at end of file
diff --git a/40/CH8/EX8.11/Exa_8_11_0.jpg b/40/CH8/EX8.11/Exa_8_11_0.jpg
new file mode 100755
index 000000000..776d7a686
--- /dev/null
+++ b/40/CH8/EX8.11/Exa_8_11_0.jpg
diff --git a/40/CH8/EX8.11/Exa_8_11_1.jpg b/40/CH8/EX8.11/Exa_8_11_1.jpg
new file mode 100755
index 000000000..e0746b696
--- /dev/null
+++ b/40/CH8/EX8.11/Exa_8_11_1.jpg
diff --git a/40/CH8/EX8.15a/Exa_8_15a.sce b/40/CH8/EX8.15a/Exa_8_15a.sce
new file mode 100755
index 000000000..5905d9dbe
--- /dev/null
+++ b/40/CH8/EX8.15a/Exa_8_15a.sce
@@ -0,0 +1,12 @@
+//overlapp-add and overlap-save methods of convolution

+//overlap-add method

+xn=[1 2 3 3 4 5];

+xon=[1 2 3];

+x1n=[3 4 5];

+hn=[1 1 1];

+yon=convol(xon,hn);

+y1n=convol(x1n,hn);

+yon=[yon,0,0,0];

+y1n=[0,0,0,y1n];

+yn=yon+y1n

+yn1=convol(xn,hn) 
\ No newline at end of file
diff --git a/40/CH8/EX8.15b/Exa_8_15b.sce b/40/CH8/EX8.15b/Exa_8_15b.sce
new file mode 100755
index 000000000..b72139b8c
--- /dev/null
+++ b/40/CH8/EX8.15b/Exa_8_15b.sce
@@ -0,0 +1,14 @@
+//(b)overlap-save method

+xn=[1 2 3 3 4 5];

+hn=[1 1 1];

+xon=[0 0 1 2 3];

+x1n=[2 3 3 4 5];

+x2n=[4 5 0 0 0];

+yon=convol(xon,hn);

+y1n=convol(x1n,hn);

+y2n=convol(x2n,hn);

+yno=yon(3:5);

+yn1=y1n(3:5);

+yn2=y2n(3:5);

+yn=[yno yn1 yn2]

+YN=convol(xn,hn)
\ No newline at end of file
diff --git a/40/CH8/EX8.16/Exa_8_16.jpg b/40/CH8/EX8.16/Exa_8_16.jpg
new file mode 100755
index 000000000..4a4bb37f1
--- /dev/null
+++ b/40/CH8/EX8.16/Exa_8_16.jpg
diff --git a/40/CH8/EX8.16/Exa_8_16.sce b/40/CH8/EX8.16/Exa_8_16.sce
new file mode 100755
index 000000000..4bd0eb54e
--- /dev/null
+++ b/40/CH8/EX8.16/Exa_8_16.sce
@@ -0,0 +1,12 @@
+//signal interpolation using FFT

+xn=[0 1 0 -1];

+XDFT=dft(xn,-1)

+ZT=[0 -2*%i 0 zeros(1:27) 0 2*%i];

+xn1=dft(ZT,1);

+t=0:1/length(xn1):1-(1/length(xn1));

+a=gca();

+a.x_location="origin";

+plot2d(t,xn1);

+xlabel('time t');

+ylabel('Amplitude');

+xtitle('Interpolated Sinusoid:4 samples over one period');
\ No newline at end of file
diff --git a/40/CH8/EX8.17/Exa_8_17.sce b/40/CH8/EX8.17/Exa_8_17.sce
new file mode 100755
index 000000000..10f457b52
--- /dev/null
+++ b/40/CH8/EX8.17/Exa_8_17.sce
@@ -0,0 +1,8 @@
+//concept of periodogram

+xn=[0 1 0 -1];

+N=4;

+XDFT=dft(xn,-1);

+for i=1:length(XDFT)

+    p(i)=(1/N)*abs(XDFT(i)^2);

+end

+p//periodogram
\ No newline at end of file
diff --git a/40/CH8/EX8.18/Exa_8_18.sce b/40/CH8/EX8.18/Exa_8_18.sce
new file mode 100755
index 000000000..c05785204
--- /dev/null
+++ b/40/CH8/EX8.18/Exa_8_18.sce
@@ -0,0 +1,9 @@
+//The DFT from the matrix formulation

+xn=[1;2;1;0];

+w=exp(-%i*%pi/2);

+for i=1:4

+    for j=1:4

+        WN(i,j)=w^((i-1)*(j-1));

+    end

+end

+XDFT=WN*xn

diff --git a/40/CH8/EX8.19/Exa_8_19.sce b/40/CH8/EX8.19/Exa_8_19.sce
new file mode 100755
index 000000000..77fcc0e9e
--- /dev/null
+++ b/40/CH8/EX8.19/Exa_8_19.sce
@@ -0,0 +1,10 @@
+//using DFT to find IDFT

+XDFT=[4;-2*%i;0;2*%i];

+XDFTc=[4;2*%i;0;-2*%i];

+w=exp(-%i*%pi/2);

+for i=1:4

+    for j=1:4

+        WN(i,j)=w^((i-1)*(j-1));

+    end

+end

+xn=1/4*(WN*XDFTc)
\ No newline at end of file
diff --git a/40/CH8/EX8.2/Exa_8_2.sce b/40/CH8/EX8.2/Exa_8_2.sce
new file mode 100755
index 000000000..39450d7f1
--- /dev/null
+++ b/40/CH8/EX8.2/Exa_8_2.sce
@@ -0,0 +1,6 @@
+//The DTFT and conjugate symmetry

+//8-point DFT

+x=[1 1 0 0 0 0 0 0];

+XDFT=dft(x,-1);

+disp(XDFT,'The DFT of x is');

+disp('from conjugate symmetry we see XDFT[k]=XDFT[8-k]');
\ No newline at end of file
diff --git a/40/CH8/EX8.20/Exa_8_20.sce b/40/CH8/EX8.20/Exa_8_20.sce
new file mode 100755
index 000000000..a87b49079
--- /dev/null
+++ b/40/CH8/EX8.20/Exa_8_20.sce
@@ -0,0 +1,9 @@
+//A four point decimation-in-frequency FFT algorithm

+x=[1 2 1 0];

+w=-%i;

+xdft(1)=x(1)+x(3)+x(2)+x(4);

+xdft(2)=x(1)-x(3)+w*(x(2)-x(4));

+xdft(3)=x(1)+x(3)-x(2)-x(4);

+xdft(4)=x(1)-x(3)-w*(x(2)-x(4));

+XDFT=dft(x,-1);

+xdft,XDFT
\ No newline at end of file
diff --git a/40/CH8/EX8.21/Exa_8_21.sce b/40/CH8/EX8.21/Exa_8_21.sce
new file mode 100755
index 000000000..0014814a8
--- /dev/null
+++ b/40/CH8/EX8.21/Exa_8_21.sce
@@ -0,0 +1,11 @@
+//A four point decimation-in-time FFT algorithm

+x=[1 2 1 0];

+w=-%i;

+xdft=[0 0 0 0];

+for i=1:4

+    for j=1:4

+        xdft(i)=xdft(i)+x(j)*w^((i-1)*(j-1));

+    end

+end

+XDFT=dft(x,-1);

+xdft,XDFT
\ No newline at end of file
diff --git a/40/CH8/EX8.22/Exa_8_22.sce b/40/CH8/EX8.22/Exa_8_22.sce
new file mode 100755
index 000000000..3cc472315
--- /dev/null
+++ b/40/CH8/EX8.22/Exa_8_22.sce
@@ -0,0 +1,9 @@
+//A 4-point DFT from a 3-point sequence

+xn=[1;2;1];

+w=exp(-%i*%pi/2);

+for i=1:4

+    for j=1:3

+        WN(i,j)=w^((i-1)*(j-1));

+    end

+end

+XDFT=WN*xn
\ No newline at end of file
diff --git a/40/CH8/EX8.23/Exa_8_23.sce b/40/CH8/EX8.23/Exa_8_23.sce
new file mode 100755
index 000000000..4a6985f9e
--- /dev/null
+++ b/40/CH8/EX8.23/Exa_8_23.sce
@@ -0,0 +1,10 @@
+//A 3-point IDFT from 4-point DFT

+XDFT=[4;-2*%i;0;2*%i];

+w=exp(-%i*%pi/2);

+for i=1:4

+    for j=1:3

+        WN(i,j)=w^((i-1)*(j-1));

+    end

+end

+WI=WN';

+xn=1/4*(WI*XDFT)
\ No newline at end of file
diff --git a/40/CH8/EX8.24/Exa_8_24.sce b/40/CH8/EX8.24/Exa_8_24.sce
new file mode 100755
index 000000000..5ad54e146
--- /dev/null
+++ b/40/CH8/EX8.24/Exa_8_24.sce
@@ -0,0 +1,24 @@
+//The importance of Periodic extension

+//(a)For M=3

+x=[1 2 1];

+XDFT=dft(x,-1)

+w=exp(-%i*2*%pi/3);

+for i=1:3

+    for j=1:3

+        WN(i,j)=w^((i-1)*(j-1));

+    end

+end

+WI=WN';

+xn=1/3*WI*XDFT

+//The result is periodic with M=3 & 1 period equals x[n]

+//(b)For M=4

+y=[1 2 1 0];

+YDFT=dft(y,-1)

+w=exp(-%i*%pi/2);

+for i=1:4

+    for j=1:4

+        WN(i,j)=w^((i-1)*(j-1));

+    end

+end

+WI=WN';

+yn=1/4*WI*YDFT

diff --git a/40/CH8/EX8.3/Exa_8_3.sce b/40/CH8/EX8.3/Exa_8_3.sce
new file mode 100755
index 000000000..fcf7eb76f
--- /dev/null
+++ b/40/CH8/EX8.3/Exa_8_3.sce
@@ -0,0 +1,24 @@
+//Circular shift and flipping

+//(a)right circular shift

+y=[1 2 3 4 5 0 0 6];

+f=y;g=y;h=y;

+for i=1:2

+    b=f(length(f));

+    for j=length(f):-1:2

+        f(j)=f(j-1);

+     end

+     f(1)=b;

+end

+disp(f,'By right circular shift y[n-2] is');

+//(b)left circular shift

+for i=1:2

+    a=g(1);

+    for j=1:length(g)-1

+        g(j)=g(j+1);

+     end

+     g(length(g))=a;

+end

+disp(g,'By left circular shift y[n+2] is');

+//(c)flipping property

+h=[h(1) h(length(h):-1:2)];

+disp(h,'By flipping property y[-n] is');
\ No newline at end of file
diff --git a/40/CH8/EX8.4/Exa_8_4.sce b/40/CH8/EX8.4/Exa_8_4.sce
new file mode 100755
index 000000000..847b1bfa2
--- /dev/null
+++ b/40/CH8/EX8.4/Exa_8_4.sce
@@ -0,0 +1,21 @@
+x=[1 2 1 0];

+XDFT=dft(x,-1)

+//(a)time shift property

+y=x;

+for i=1:2

+    a=y(1);

+    for j=1:length(y)-1

+        y(j)=y(j+1);

+     end

+     y(length(y))=a;

+end

+YDFT=dft(y,-1)

+disp(YDFT,'By Time-Shift property DFT of x[n-2] is');  

+//(b)flipping property

+g=[x(1) x(length(x):-1:2)]

+GDFT=dft(g,-1)

+disp(GDFT,'By Time reversal property DFT of x[-n] is');  

+//(c)conjugation property

+p=XDFT;

+PDFT=[p(1);p(4:-1:2)];

+disp(YDFT,'BY conjugation property DFT of x*[n] is');  

diff --git a/40/CH8/EX8.5a/Exa_8_5a.sce b/40/CH8/EX8.5a/Exa_8_5a.sce
new file mode 100755
index 000000000..63e5aa5a4
--- /dev/null
+++ b/40/CH8/EX8.5a/Exa_8_5a.sce
@@ -0,0 +1,42 @@
+//properties of DFT

+//a1)product

+xn=[1 2 1 0];

+XDFT=dft(xn,-1)

+hn=xn.*xn

+HDFT=dft(hn,-1)

+HDFT1=1/4*(convol(XDFT,XDFT))

+HDFT1=[HDFT1,zeros(8:12)];

+HDFT2=[HDFT1(1:4);HDFT1(5:8);HDFT1(9:12)];

+HDFT3=[0 0 0 0];

+for i=1:4

+    for j=1:3

+        HDFT3(i)=HDFT3(i)+HDFT2(j,i);

+    end

+end

+disp(HDFT3,'DFT of x[n]^2 is');

+//a2)periodic convolution

+vn=convol(xn,xn);

+vn=[vn,zeros(8:12)];

+vn=[vn(1:4);vn(5:8);vn(9:12)];

+vn1=[0 0 0 0];

+for i=1:4

+    for j=1:3

+        vn1(i)=vn1(i)+vn(j,i);

+    end

+end

+VDFT=dft(vn1,-1);

+VDFT1=XDFT.*XDFT;

+disp(VDFT1,'DFT of x[n]*x[n] is');

+//a3)signal energy(parcewell's theorem)

+xn2=xn^2;

+E=0;

+for i=1:length(xn2)

+    E=E+abs(xn2(i));

+end

+XDFT2=XDFT^2

+E1=0;

+for i=1:length(XDFT2)

+    E1=E1+abs(XDFT2(i));

+end

+E,(1/4)*E1;

+disp(1/4*E1,'The energy of the signal is');
\ No newline at end of file
diff --git a/40/CH8/EX8.5b/Exa_8_5b.sce b/40/CH8/EX8.5b/Exa_8_5b.sce
new file mode 100755
index 000000000..05c7e80c0
--- /dev/null
+++ b/40/CH8/EX8.5b/Exa_8_5b.sce
@@ -0,0 +1,42 @@
+//b1)modulation

+XDFT=[4 -2*%i 0 2*%i];

+xn=dft(XDFT,1)

+for i=1:length(xn)

+    zn(i)=xn(i)*%e^((%i*%pi*(i-1))/2);

+end

+disp(zn,'The IDFT of XDFT[k-1] is');

+ZDFT=[2*%i 4 -2*%i 0];

+zn1=dft(ZDFT,1)

+//b2)periodic convolution

+HDFT=(convol(XDFT,XDFT))

+HDFT=[HDFT,zeros(8:12)];

+HDFT=[HDFT(1:4);HDFT(5:8);HDFT(9:12)];

+HDFT1=[0 0 0 0];

+for i=1:4

+    for j=1:3

+        HDFT1(i)=HDFT1(i)+HDFT(j,i);

+    end

+end

+HDFT1;

+hn=dft(HDFT1,1)

+hn1=4*(xn.*xn);

+disp(hn1,'The IDFT of XDFT*XDFT is');

+//b3)product

+WDFT=XDFT.*XDFT;

+wn=dft(WDFT,1)

+wn1=convol(xn,xn);

+wn1=[wn1,zeros(8:12)];

+wn1=[wn1(1:4);wn1(5:8);wn1(9:12)];

+WN=[0 0 0 0];

+for i=1:4

+    for j=1:3

+        WN(i)=WN(i)+wn1(j,i);

+    end

+end

+disp(WN,'The IDFT of XDFT.XDFT is');

+//b4)Central ordinates and signal Energy

+E=0;

+for i=1:length(xn)

+    E=E+abs(xn(i)^2);

+end

+disp(E,'the signal energy is'); 
\ No newline at end of file
diff --git a/40/CH8/EX8.5c/Exa_8_5c.sce b/40/CH8/EX8.5c/Exa_8_5c.sce
new file mode 100755
index 000000000..bc4c62f5d
--- /dev/null
+++ b/40/CH8/EX8.5c/Exa_8_5c.sce
@@ -0,0 +1,7 @@
+//Regular convolution

+xn=[1 2 1 0];

+yn=[1 2 1 0 0 0 0];

+YDFT=dft(yn,-1)

+SDFT=YDFT.*YDFT

+sn=dft(SDFT,1)

+sn1=convol(xn,xn)
\ No newline at end of file
diff --git a/40/CH8/EX8.6/Exa_8_6.sce b/40/CH8/EX8.6/Exa_8_6.sce
new file mode 100755
index 000000000..be5c3cbb9
--- /dev/null
+++ b/40/CH8/EX8.6/Exa_8_6.sce
@@ -0,0 +1,20 @@
+//Signal and spectrum replication

+xn=[2 3 2 1];

+XDFT=dft(xn,-1)

+yn=[xn xn xn];

+YDFT=dft(yn,-1)

+YDFT1=3*[XDFT(1:1/3:length(XDFT))];

+for i=2:3

+    YDFT1(i:3:length(YDFT1))=0;

+end

+YDFT1(12:-1:11)=0;

+disp(YDFT1,'the DFT of x[n/3] is');

+hn=[xn(1:1/3:length(xn))]

+for i=2:3

+    hn(i:3:length(hn))=0;

+end

+hn(12:-1:11)=0;

+hn

+HDFT=dft(hn,-1)

+HDFT1=[XDFT;XDFT;XDFT];

+disp(HDFT1,'the DFT of y[n]=[x[n],x[n],x[n]] is');
\ No newline at end of file
diff --git a/40/CH8/EX8.7/Exa_8_7.sce b/40/CH8/EX8.7/Exa_8_7.sce
new file mode 100755
index 000000000..9d9c9e16d
--- /dev/null
+++ b/40/CH8/EX8.7/Exa_8_7.sce
@@ -0,0 +1,7 @@
+//relating DFT and IDFT

+XDFT1=[4 -2*%i 0 2*%i];

+xn1=dft(XDFT1,1);

+disp(xn1,'The IDFT of XDFT1');

+XDFT2=[12 -24*%i 0 4*%e^(%i*%pi/4) 0 4*%e^(-%i*%pi/4) 0 24*%i];

+xn2=dft(XDFT2,1);

+disp(xn2,'The IDFT of XDFT1'); 
\ No newline at end of file
diff --git a/40/CH8/EX8.8/Exa_8_8.sce b/40/CH8/EX8.8/Exa_8_8.sce
new file mode 100755
index 000000000..7fad7f114
--- /dev/null
+++ b/40/CH8/EX8.8/Exa_8_8.sce
@@ -0,0 +1,9 @@
+//Relating DFT and DTFT

+xn=[1 2 1 0];

+XDFT=dft(xn,-1);

+//for F=k/4,k=0,1,2,3

+for k=1:4

+    XF(k)=1+2*%e^(-%i*%pi*(k-1)/2)+%e^(-%i*%pi*(k-1));

+end

+XF,XDFT

+disp(XF,'The DFT of x[n] is');

diff --git a/40/CH8/EX8.9a/Exa_8_9a.sce b/40/CH8/EX8.9a/Exa_8_9a.sce
new file mode 100755
index 000000000..b61b2c4d9
--- /dev/null
+++ b/40/CH8/EX8.9a/Exa_8_9a.sce
@@ -0,0 +1,15 @@
+//DFT and DFS of sinusoids

+n2=0:0.5/1000:5.5/100;

+xt=4*cos(100*%pi*n2');

+n=0:(0.5)/100:(5.5)/100;//F=3/12 hence N=12

+xn=4*cos(100*%pi*n');

+XDFT=dft(xn,-1);

+n1=0:11;

+a=gca();

+a.x_location="origin";

+plot2d(n2,xt);

+plot2d3('gnn',n,xn);

+xset('window',1);

+b=gca();

+b.x_location="origin";

+plot2d3('gnn',n1,XDFT);

diff --git a/40/CH8/EX8.9a/Exa_8_9a_0.jpg b/40/CH8/EX8.9a/Exa_8_9a_0.jpg
new file mode 100755
index 000000000..7d2fad5b0
--- /dev/null
+++ b/40/CH8/EX8.9a/Exa_8_9a_0.jpg
diff --git a/40/CH8/EX8.9a/Exa_8_9a_1.jpg b/40/CH8/EX8.9a/Exa_8_9a_1.jpg
new file mode 100755
index 000000000..b0bd756d8
--- /dev/null
+++ b/40/CH8/EX8.9a/Exa_8_9a_1.jpg
diff --git a/40/CH8/EX8.9b/Exa_8_9b.sce b/40/CH8/EX8.9b/Exa_8_9b.sce
new file mode 100755
index 000000000..d32e7094c
--- /dev/null
+++ b/40/CH8/EX8.9b/Exa_8_9b.sce
@@ -0,0 +1,15 @@
+//DFT and DFS of sinusoids

+n2=0:1/1280:31/128;

+xt=4*sin(72*%pi*n2');

+n=0:1/128:31/128;//F=9/32 hence N=32

+xn=4*sin(72*%pi*n');

+XDFT=abs(dft(xn,-1));

+n1=0:31;

+a=gca();

+a.x_location="origin";

+plot2d(n2,xt);

+plot2d3('gnn',n,xn);

+xset('window',1);

+b=gca();

+b.x_location="origin";

+plot2d3('gnn',n1,XDFT);

diff --git a/40/CH8/EX8.9b/Exa_8_9b_0.jpg b/40/CH8/EX8.9b/Exa_8_9b_0.jpg
new file mode 100755
index 000000000..3ae80d7a6
--- /dev/null
+++ b/40/CH8/EX8.9b/Exa_8_9b_0.jpg
diff --git a/40/CH8/EX8.9b/Exa_8_9b_1.jpg b/40/CH8/EX8.9b/Exa_8_9b_1.jpg
new file mode 100755
index 000000000..e757639cc
--- /dev/null
+++ b/40/CH8/EX8.9b/Exa_8_9b_1.jpg
diff --git a/40/CH8/EX8.9c/Exa_8_9c.sce b/40/CH8/EX8.9c/Exa_8_9c.sce
new file mode 100755
index 000000000..67632bb96
--- /dev/null
+++ b/40/CH8/EX8.9c/Exa_8_9c.sce
@@ -0,0 +1,15 @@
+//DFT and DFS of sinusoids

+n2=0:1/840:6/21;

+xt=4*sin(72*%pi*n2')-6*cos(12*%pi*n2');

+n=0:1/21:6/21;//F=3/12 hence N=12

+xn=4*sin(72*%pi*n')-6*cos(12*%pi*n');

+XDFT=abs(dft(xn,-1));

+n1=0:6;

+a=gca();

+a.x_location="origin";

+plot2d(n2,xt);

+plot2d3('gnn',n,xn);

+xset('window',1);

+b=gca();

+b.x_location="origin";

+plot2d3('gnn',n1,XDFT);

diff --git a/40/CH8/EX8.9c/Exa_8_9c_0.jpg b/40/CH8/EX8.9c/Exa_8_9c_0.jpg
new file mode 100755
index 000000000..924bb1475
--- /dev/null
+++ b/40/CH8/EX8.9c/Exa_8_9c_0.jpg
diff --git a/40/CH8/EX8.9c/Exa_8_9c_1.jpg b/40/CH8/EX8.9c/Exa_8_9c_1.jpg
new file mode 100755
index 000000000..55efa132d
--- /dev/null
+++ b/40/CH8/EX8.9c/Exa_8_9c_1.jpg
diff --git a/40/CH8/EX8.9d/Exa_8_9d.sce b/40/CH8/EX8.9d/Exa_8_9d.sce
new file mode 100755
index 000000000..2d5d4b294
--- /dev/null
+++ b/40/CH8/EX8.9d/Exa_8_9d.sce
@@ -0,0 +1,15 @@
+//DFT and DFS of sinusoids

+n2=0:1/2400:23/240;

+xt=1+4*sin(120*%pi*n2')+4*sin(40*%pi*n2');

+n=0:1/240:23/240;//F=9/32 hence N=32

+xn=1+4*sin(120*%pi*n')+4*sin(40*%pi*n');

+XDFT=abs(dft(xn,-1));

+n1=0:23;

+a=gca();

+a.x_location="origin";

+plot2d(n2,xt);

+plot2d3('gnn',n,xn);

+xset('window',1);

+b=gca();

+b.x_location="origin";

+plot2d3('gnn',n1,XDFT);
\ No newline at end of file
diff --git a/40/CH8/EX8.9d/Exa_8_9d_1.jpg b/40/CH8/EX8.9d/Exa_8_9d_1.jpg
new file mode 100755
index 000000000..baec0a646
--- /dev/null
+++ b/40/CH8/EX8.9d/Exa_8_9d_1.jpg
diff --git a/40/CH8/EX8.9d/exa_8_9d_0.jpg b/40/CH8/EX8.9d/exa_8_9d_0.jpg
new file mode 100755
index 000000000..2d0969b63
--- /dev/null
+++ b/40/CH8/EX8.9d/exa_8_9d_0.jpg