I dislike education acronyms, but I can make exceptions for mathematical ones.  One of my favourite topics in A-level Maths is full to bursting with them: DRVs, CRVs, PDF, CDF.  This is a visual representation of the CDF (cumulative distribution function) of a CRV (continuous random variable), which is the function for the area under the curve from x=-∞ to any other value, a, or more specifically, P(X<a).  Take note of the syntax for piecewise functions.

The PDF (probability density function) of the CRV I’ve used* is


and its CDF is


But you don’t need to know the CDF to represent it in Desmos, you just need to use inequalities to shade the region between the x-axis and the curve, with a slider for the variable value of x.  The syntax is a little unusual, but take a look and you’ll see how it’s done.  The same principle was used in my model for normal distribution.


*It’s taken from the Edexcel S2 exam, June 2012, question 7.