I was most impressed with the Desmos Graphing Calculator last year. It’s a powerful and user friendly graphical calculator.
It’s just been re-written from the ground up in HTLM5 which means it will work perfectly on an iPad or other tablet. It’s genuinely impressive and exciting to see what magic coders are starting to weave with HTML5.
Head over to https://www.abettercalculator.com/c on any device to try it out for yourself.