Just go to a google search bar and type in a function.
For instance, cos(pi*x/5)
You'll get a graph that has some interactive features.
Separate multiple functions with commas.
More like this
Agonist (via Melissa and
John Scalzi has an interesting post this morning (well, interesting if you're a writer anyway) about the use of punctuation, prompted by a little battle he is having with the copy editor for his new book.
A trip through the wires tubes that are the Internets:
Interesting AND cool.