Naiku now uses the Demos calculators. You have three options to choose from: Four Function, Scientific Calculator, and Graphing Calculator. You can learn about and how to use each of these calculators at learn.desmos.com.
When creating or editing a test, you have the option of picking a calculator for each item. Now, rather than having two choices (basic and scientific) like before, you have three to choose from. Recall, this is how you select which calculator you want to appear on each item. Below, the Basic Calculator has been selected for Item 1, the Scientific Calculator has been selected for Item 2, and the Graphing Calculator has been selected for Item 3.
Here is the Desmos Basic Calculator in Naiku.
Here is the Desmos Scientific Calculator in Naiku.
Here is the Desmos Graphing Calculator in Naiku.