Make sure you're logged into your account, and then head on over to your Subscription Management Page under your account settings. Click on the 'Subscribe' button and detailed instructions will follow.

For the Web subscription, log in to your account and visit: Subscription Management Page. Click the 'Cancel' button and detailed instructions will follow.

If you subscribed within the mobile apps, you need to cancel with Apple or Google, because they handle mobile payments.

For the iOS mobile app, follow these instructions to cancel with Apple: View, change, or cancel your Apple subscriptions

For the Android mobile app, follow these instructions to cancel with Google: Cancel, pause, or change a subscription on Google Play

Check out our symbols tutorial for a list of symbols that the calculator can understand. Here are a few common symbols:
+ (Addition)
- (Subtraction)
* (Multiplication)
/ (Division)
^ (Exponent: "raised to the power")
sqrt (Square Root) (Example: sqrt(9))
pi (Pi)

Yes, you can login to the mobile app with your upgraded web account to access the premium app.