Install libqalculate-doc by entering the following commands in the terminal:
sudo apt update sudo apt install libqalculate-doc
Powerful and easy to use desktop calculator - documentation
Qalculate! is small and simple to use but with much power and versatility underneath. Features include customizable functions, units, arbitrary precision, plotting, and a graphical interface that uses a one-line fault-tolerant expression entry (although it supports optional traditional buttons). . This package contains the libqalculate documentation for developers.