My desire is that everything on this website (except in the store) shall remain free of obligatory cost to all who visit.
I am also determined that the site shall remain advertising free.
Please donate as you are able and in a manner that you think is reasonable for what you have been able to obtain from my work.
Thank you very much for your support!
Wow, how useful. … I always had a hard time with the chain rule, until I watched this video. The right presentation makes all the difference. Thank you very much. … These 20 second math videos you’ve graciously posted are excellent. I’m my little corner of the world, you’ve done great things.
avaratatat (on a CCM YouTube video about the Chain Rule)
See all Testimonials