91 - Links of interest

Geogebra
GeoGebra is an interactive geometry, algebra, statistics and calculus application, intended for learning and teaching mathematics and science from primary school to university level. GeoGebra is available on multiple platforms with its desktop applications for Windows, macOS and Linux, with its tablet apps for Android, iPad and Windows, and with its web application based on HTML5 technology.
Its creator, Markus Hohenwarter,[1] started the project in 2001 (as part of his master's thesis) at the University of Salzburg, continuing it at Florida Atlantic University (2006–2008), Florida State University (2008–2009), and now at the University of Linz together with the help of open-source developers and translators all over the world.

Wolfram Alpha
WolframAlpha (also styled Wolfram|Alpha) is a computational knowledge engine or answer engine developed by Wolfram Alpha LLC, a subsidiary of Wolfram Research. It is an online service that answers factual queries directly by computing the answer from externally sourced "curated data", rather than providing a list of documents or web pages that might contain the answer as a search engine might.
WolframAlpha, which was released on May 18, 2009, is based on Wolfram's earlier flagship product Wolfram Mathematica, a computational platform or toolkit that encompasses computer algebra, symbolic and numerical computation, visualization, and statistics capabilities.

Symbolab
Symbolab was released in late 2011 by three Israelis, Michal Avny (CEO), Adam Arnon (Chief Scientist) and Lev Alyshayev (CTO). They created an engine which can interpret a user-entered equation or symbolic problem and find the solution if it exists. Then they added the ability to show all the steps explaining the calculation.