# How to add a condition to a formula so that it will not appear at the result? [duplicate]

Sometimes I have very long and complicated equations, when I evaulate the equations for example taking derivative or integral there will be several conditions with the answer. My question is that; is there any way that I enter the conditions at the begining of the program so that so that it will not appear in the evaluation result?

I will give a simple example:

pdf = x^(L-1)/( γ^L Gamma[L]) Exp[(-x)/γ];
Re[L] > 0;

Integrate[ pdf, {x, 0, γ}]

ConditionalExpression[ (Gamma[L]-Gamma[L,1])/(Gamma[L]),  Re[L] > 0 ]


in the above example even if I write the condition which is Re[L] > 0, it will appear again at the result of evaluation.

• Most likely you are looking for ways of imposing assumptions. This question is closely related: How to specify assumptions before evaluation? or simply a duplicate. Sep 10, 2013 at 10:38
• thanks for the answers. my question is is specifically that; is there anyway to write conditions at the begining of the program so that you don't need every time repeat them with your equations. Sep 10, 2013 at 11:25
• Have you read answers to the linked question? Namely you need $Assumptions = Re[L] > 0 and appropriately writing your integral. Sep 10, 2013 at 11:50 • Hi Artes, that was the answer of my question. $Assumptions = Re[L] > 0 you can write all your conditions at the begining of the program like this: \$Assumptions = Re[b] > 0 && Re[Sqrt[b]] > 0; by putting && between your conditions. Thanks Sep 10, 2013 at 15:30

Yes, you can use Assuming, eg. for your particular example:
Assuming[{Re[L] > 0},

1 - Gamma[L, 1]/Gamma[L]
cdf = Integrate[pdf, {x, 0, \[Gamma]}, GenerateConditions -> False]