### 7.4.20 Cumulative distribution functions: cdf

The cdf command will take as arguments the name of a probability distribution, along with any needed parameters, and return an expression for the cumulative distribution function. If you enter

cdf(normald,0,1)

you will get

(erf(x*sqrt(2)/2)+1)/2

You can evaluate the cumulative distribution function at a value by adding the value as an argument; if you enter

cdf(binomial,10,0.5,4)

you will get

0.376953125