A graphing calculator built from scratch — its own expression parser, its own symbolic differentiation, its own plotter. No libraries.
x^2
y = x^2
f(x) = x^2
2x
3sin(x)
(x+1)(x-1)
sin cos tan
asin acos atan
sec csc cot
sinh cosh tanh
ln(x)
log(x)
log2(x)
sqrt(x)
cbrt(x)
exp(x)
x^(1/3)
abs(x)
|x|
floor ceil round sign
pi
e
tau
phi
π
√
1/2x
(1/2)·x
Derivative draws the tangent at a point you can drag, and — with the limit definition switched on — the secant through (a, f(a)) and (a+h, f(a+h)). Shrink h and watch the difference quotient converge on f′(a). Derivatives are computed symbolically where the rules apply, and by a limit where they don't.
Integral builds the Riemann sum for an interval you can drag, under any of four rules. The exact value comes from adaptive Simpson integration, so the error column tells you how far off the approximation really is — and how quickly each rule converges as n grows.
Your work is saved in this browser automatically. The link button copies a URL that carries the whole session with it, and the download button saves the graph as a PNG at twice screen resolution.