problem 3 started

nin13001 · Dec 6, 2017 · ad5e7ed · ad5e7ed
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diff --git a/README.md b/README.md
@@ -47,3 +47,23 @@ y(1)=y0;
 end
 ```
 ![](assets/README-23f54e97.png)
+
+# Problem 3
+## Part A
+The analytical solution is y = cos(3t)
+
+## Part B
+```
+dt=[.1 .001];
+figure();
+hold on
+x=[0:dt(2):3]';
+y_n=zeros(length(x),2);
+y_n(1,:)=[1,0];
+for i=2:length(x)
+        dy=prob3_ode(x,y_n(i-1,:));
+        y_n(i,:)=y_n(i-1,:)+ dt(2)*dy;
+end
+plot(x,cos(3*x),'k-',x,y_n(:,1),'o');
+```
+![](assets/README-4e4bb548.png)
diff --git a/assets/README-4e4bb548.png b/assets/README-4e4bb548.png
diff --git a/prob3_ode.m b/prob3_ode.m
@@ -0,0 +1,5 @@
+function dy=prob3_ode(t,y)
+dy=zeros(size(y));
+dy(1)=y(2);
+dy(2)=-9*y(1);
+end
diff --git a/prob3ptB.m b/prob3ptB.m
@@ -0,0 +1,11 @@
+dt=[.1 .001];
+figure();
+hold on
+x=[0:dt(2):3]';
+y_n=zeros(length(x),2);
+y_n(1,:)=[1,0];
+for i=2:length(x)
+        dy=prob3_ode(x,y_n(i-1,:));
+        y_n(i,:)=y_n(i-1,:)+ dt(2)*dy;
+end
+plot(x,cos(3*x),'k-',x,y_n(:,1),'o');