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May 26th, 2013, 02:47 AM  #1 
Member Joined: Apr 2013 Posts: 42 Thanks: 1  probability of X and Y
The joint propability function of X and Y is given by . So far I found . I still need to find and . The answer should be and , respectively. But I do not see how to get there. For the first I take the double integral over 2 with and . For the second I take boundaries and . The answer I get are 1 and 0. Why is this wrong and how should it be done? 
May 26th, 2013, 03:02 AM  #2 
Member Joined: Apr 2013 Posts: 42 Thanks: 1  Re: probability of X and Y
Now I took . I made a graph of and took the boundaries and . That gave me , so the first one is solved 
May 26th, 2013, 03:13 AM  #3 
Member Joined: Apr 2013 Posts: 42 Thanks: 1  Re: probability of X and Y
And a sketch also did the work for the other question. I took and and that gave me indeed the right answer. Sorry for bothering and thanks anyway! 
May 26th, 2013, 03:46 AM  #4 
Math Team Joined: Nov 2010 From: Greece, Thessaloniki Posts: 1,990 Thanks: 133 Math Focus: pre pre pre pre pre pre pre pre pre pre pre pre calculus  Re: probability of X and Y [color=#000000]It is much easier to make the probability computations using area computation. [attachment=0:m6xn6toy]george.png[/attachment:m6xn6toy] [/color] 
May 26th, 2013, 04:03 AM  #5 
Member Joined: Apr 2013 Posts: 42 Thanks: 1  Re: probability of X and Y
The graph indeed makes it perfectly clear. I'll remember the tip for other questions/problems. Thanks a lot!


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