From cdf to pdf

Posted by Chinni18 on
URL: http://discussion-forum.276.s1.nabble.com/From-cdf-to-pdf-tp7578030.html

I have a very silly and basic doubt but it's really bugging me:
The distribution function for a random variable X is F(x) = [1-{e^(-2x)}] if x>or=o
                                                                               and o if x<0
To find the density function, f (x) we do d/dx F(x) = 2[e^(- 2x) if x> 0 and o if x<0
My doubt is how did the sign in the bold change from a weak to strict inequality for a density function?
Would appreciate any inputs