PowCalc its a powerful calculator with many expressions (trigonometric, logarithmic, statistics, etc.) and also vector and matrix calculus. It can evaluate complex expressions and combine them together in a very simple way.
You can also save in the cloud user defined functions to be used from all your devices.
With PowCalc you can also plot functions (also x-y parametric functions) and numerically evaluate integrals, extremes, zeroes, etc.
Moreover you can make common conversion between unit of measurements.