# Math Help - PDF and CDF

1. ## PDF and CDF

Let X be a continuous random variable with PDF fX(x) = ce^{-|x|}

Let Y = |X|. Find the CDF of Y and deduce its PDF

I have gotten 1-e^-y for y>=0 as the cdf

someone showed me what they got which is sinhy;The problem that i see with this is that we need limit as the CDF approaches 0 to be zero which this fulfils, but also the limit as the cdf approaches infinity to be one which this does not fulfil. Anyway if someone could check what they get as a solution i would appreciate it.

2. Originally Posted by ulysses123
Let X be a continuous random variable with PDF fX(x) = ce^{-|x|}

Let Y = |X|. Find the CDF of Y and deduce its PDF

I have gotten 1-e^-y for y>=0 as the cdf Mr F says: I get this too.

someone showed me what they got which is sinhy;The problem that i see with this is that we need limit as the CDF approaches 0 to be zero which this fulfils, but also the limit as the cdf approaches infinity to be one which this does not fulfil. Anyway if someone could check what they get as a solution i would appreciate it.
To specify the cdf completely you need to add that cdf = 0 for y < 0.