Calculus is a "must have" tool for definite and indefinite integrals. Not only a quick reference list for the important formulas, but a calculator that allows you to evaluate (solve) the integral. A calculator (enter upper/lower limits and any constants) pops up for quick entry and calculation.

Engineering Units converter

King James Version

Mathpro is a collection of calculators: Matrix Calculator (including complex matrices), Complex Number Calculator, Factorial Calculator, Quadratic Equation Solver, Cubic Equation Solver, Exponent Calculator, Nth Root Calculator, Vector Calculator and Simultaneous Equation Solver.