chessguy | this might be helpful http://en.wikipedia.org/wiki/Joint_probability_density_function#Probability_function_associated_to_multiple_variables |

MrFreak | yeah i'm reading that right now I guess it would be like Pr(x >= 0, 0 <= y <= e^-x) Integral 0 to infinity Integral 0 to 1 e^-x dx dy? does that look right? |

kmh | MrFreak : well do you have info for outside the region ? |

MrFreak | info for outside the region? i assume outside the region is always 0 |

kmh | the probabilty outside the region is 0 ? ah ok you need an interval for x though as the area under the curve needs to be limited or bounded rather |

MrFreak | interval for x would be 0 to infinity i think |

kmh | hmmm yes if the improper integral exists that's good enough |

MrFreak | e^-x approaches 0 asymptotically |

kmh | but you need the area under the curve first so that you can norm the measure to 1 oh it is 1 anyway :) |

MrFreak | so how do i set up the integral for the area under the curve? |

jhardin | quick question, can anyone think of any hermitian unitary matrices that aren't just a string of +-i's along the diagonal, or antidiagonal err, anti-hermitian |

kmh | MrFreak : i*m a bit rusty too with n-dim distribution, but i think it looks like that P(X<x,Y<y)=int(int(1_[0,e^(-x)](u),u=0..y),v=0..x) and 1_[0,e^(-x)](u) is the indicator function |

MrFreak | hmm |

Copter | X_n+1= 3X_n/ (X_n^2+X_n+1), Xn=2007. I wanted to prove that its bounded above by 1. So I did X_n+1 <=1 , 3X_n/ (X_n^2+X_n+1) <=1 and reached (X_n-1)^2 >=0 which is true. Can I conclude Xn is bounded by 1 from above? :o ne1? :P |

MrFreak | so how simplyy do i find the area under the curve y = e^-x from x = 0 to infinity? the joint density will just be 1/area, since it's uniformly distributed integral from 0 to infinity of e^-x? |

chessguy | that's just a simple improper integral |

MrFreak | heh, i'm a CS major, and the last time i did an integral was calc 3 two years ago |

chessguy | take the limit as M goes to infinity of the integral from 0 to M |

MrFreak | i sort of hazily remember the terms integration by parts and u substitution |

chessguy | i was a CS major too :) |