I wrote before about Marvin Bittinger, a mathematician who made up an entirely bogus "time principle" to estimate probabilities of events. And about Kirk Durston, who speaks confidently about infinity, but gets nearly everything wrong.
And here's yet another example: creationist Jonathan Bartlett, who is director of something called the Blyth Institute (which, mysteriously, lists no actual people associated with it, and seems to consist entirely of Jonathan Bartlett himself), has recently published a post about mathematics, in which he makes a number of very dubious assertions. I'll just mention two.
First, Bartlett calls polynomials the "standard algebraic functions". This is definitely nonstandard terminology, and not anything a mathematician would say. For mathematicians, an "algebraic function" is one that satisfies the analogue of an algebraic equation. For example, consider the function f(x) defined by f^2 + f + x = 0. The function (-1 + sqrt(1-4x))/2 satisfies this equation, and hence it would be called algebraic.
Second, Bartlett claims that "every calculus student learns a method for writing sine and cosine" in terms of polynomials, even though he also states this is "impossible". How can one resolve this contradiction? Easy! He explains that "If, however, we allow ourselves an infinite number of polynomial terms, we can indeed write sine and cosine in terms of polynomial functions".
This reminds me of the old joke about Lincoln: "In discussing the question, he used to liken the case to that of the boy who, when asked how many legs his calf would have if he called its tail a leg, replied, "Five," to which the prompt response was made that calling the tail a leg would not make it a leg."
If one allows "an infinite number of polynomial terms", then the result is not a polynomial! How hard can this be to understand? Such a thing is called a "power series"; it is not the same as a polynomial at all. Mathematicians even use a different notation to distinguish between these. Polynomials over a field F in one variable are written using the symbol F[x]; power series are written as F[[x]].
Moral of the story: don't learn mathematics from creationists.
P.S. Another example of Bartlett getting basic things wrong is here.