The iPhone and iPod touch includes a built-in calculator app that’s easy to use and handy since it goes where ever you take your pocket-size iOS device. That calculator is pretty basic, but it also hides a full-featured scientific calculator, and all it takes to find it is a little twist.

You can even ask Siri to perform calculations for you, long-press on results to copy them, long-press the field to paste numbers in, and swipe left or right above the keypad to delete digits one by one.

For those of you who haven’t found it yet, open Calculator, then rotate your iPhone from portrait to landscape orientation. The app will switch to scientific mode automatically, and you can use it to perform logarithms, square roots, trigonometric calculations, and more advanced math equations. To switch back to the regular calculator, rotate your phone to portrait mode.

If you can’t get the scientific calculator to show up, make sure the portrait orientation lock is disabled. On iPhone models with Touch ID, you’ll know the screen is locked by its status bar icon, the lock symbol within a circular arrow.