Approximate $\int_a^b f(x)\,dx$ with equal-width rectangles. Choose left endpoints, midpoints, or right endpoints. Expression rules match the other calculus tools (constrained parser — no arbitrary code).
Riemann sum integrator
What it computes. A rectangular partition estimate of a definite integral.
Limitations. Discontinuities, huge $n$, or stiff oscillations reduce reliability. Not symbolic integration. See the disclaimer.
Related: Definite integral · Integral · Calculus foundations · Numerical derivative