Mathematica 9 is now available
Student Support Forum
-----
Student Support Forum: 'Integration' topicStudent Support Forum > General > "Integration"

Next Comment >Help | Reply To Topic
Author Comment/Response
Sinval Santos
05/06/02 08:50am

To integrate Sqrt[y-k*x^2] , in relation to x

First: to substitute k after the integration

In[1]:=w1=Integrate[Sqrt[y-k*x^2],x]/.k->2//FullSimplify
Out[1]=(1/4)*(2*x*Sqrt[-2*x^2+y]+I*Sqrt[2]*y*Log[2*(-I*Sqrt[2]*x+ Sqrt[-2*x^2+y])])

In[2]:=w1/.{x->1,y->20}//N
Out[2]=4.39644+15.4928*I (Complex)

Second: to substitute k before the integration

In[1]:=w2=Integrate[(Sqrt[y-k*x^2]/.k->2),x]//FullSimplify
Out[1]=w2=(1/4)*(2*x*Sqrt[-2*x^2+y]+Sqrt[2]*y*ArcTan[(Sqrt[2]*x)/ Sqrt[-2*x^2+y]])

In[2]:=w2/.{x->1,y->20}//N
Out[2]=4.39644 (Real)

Because different results ?
How to avoid this, in symbolic calculation ?


URL: ,

Subject (listing for 'Integration')
Author Date Posted
Integration Sinval Santos 05/06/02 08:50am
Re: Integration Henry Lamb 05/14/02 04:24am
Next Comment >Help | Reply To Topic