What the app does
Your input is turned into an expression tree, tidied up, and printed back. Implicit multiplication, the unicode minus pasted from a textbook, |x| for absolute value and sin²(x) for the square of a sine are all accepted, so what you type need not be typed the way a computer would write it.
Why it matters
Everything that follows is computed from that tree. If the reading is wrong, so is the whole study — which is why the tidied form is shown back to you first.
Read further
- Function (mathematics) Wikipedia
- Elementary function Wikipedia
- Review of functions OpenStax Calculus