iOS App
Q.E.D
The history of mathematics, read as a story.
Q.E.D. stands for the Latin quod erat demonstrandum — which was to be demonstrated. This app is a reader's companion to the history of mathematics: the great theorems, and the people who proved them. Instead of following formulas, every entry is told in plain language: what it says, why it matters, and the idea behind the proof. Whether you love mathematics or drifted away from it at school, each entry is a satisfying ten-minute read.
🔒 Works entirely offline. It needs no connection, collects nothing about you, and shows no ads.
Read the privacy policyWhat's inside
Theorems and turning points
From ancient Greece to the present day, arranged by era: Antiquity, Medieval and Renaissance, and the 17th through 21st centuries. New entries arrive with each update.
The mathematicians
Thales, Pythagoras, Euler, Gauss, Galois, Ramanujan — and Hypatia, Ada Lovelace, Kovalevskaya, and the Japanese tradition of Seki Takakazu, Teiji Takagi, and Kenkichi Iwasawa.
English and Japanese
Every word — entries, biographies, detailed proofs — is written in both languages, and the app follows your device's language setting.
Features
Theorem of the Day
A new theorem on your home screen every day, so you never have to decide where to start.
Timeline of Mathematics
Twenty-six centuries of ideas on a single scrolling timeline, era by era.
Gentle explanations
Each entry in four parts: What does it say? An everyday analogy. Why it matters. The idea behind the proof.
Animated diagrams
Step through the Pythagorean theorem, the sieve of Eratosthenes, the diagonal argument, the Koch curve and more — one move at a time, or played straight through.
The Proof in Detail
An expandable, thorough walkthrough for every entry, for when you want to go deeper.
The Drama Behind It
The mathematical duel of Cardano and Tartaglia, Galois's last night, Wiles's seven years and the gap in his proof — the human stories standing behind the theorems.
Places
Birthplaces and workplaces of the great mathematicians, shown on a map.
Search and bookmarks
Find any theorem, person, or keyword in an instant, and save the ones you want to return to.
Price
- Free. Every entry is open, from the first page to the last.
- No advertising of any kind.
- The only in-app purchase is an optional consumable tip, for anyone who wants to support the work. It unlocks nothing whatsoever.
Requirements
Runs on iPhone with iOS 18.0 or later. Everything is bundled with the app, so it reads the same in airplane mode or out of signal.
Read the privacy policy