https://calc21.com/Calc21 — calculus in the 21st centuryNew calculus articles for high-school teachers and the wider calculus community.2026-10-19T00:00:00ZCalc21https://calc21.com/Editorial content: cite Calc21 with a link.https://calc21.com/is-calculus-worth-itIs calculus still worth learning in the AI era?2026-10-19T00:00:00Z2026-10-19T00:00:00ZThe honest case on each side: what a tool has made cheap, what it has not, the three questions that decide whether a calculus course still earns its hours, and what would change our mind.Calc21https://calc21.com/ai-in-calculusAI in calculus: five uses worth allowing, three traps2026-10-18T00:00:00Z2026-10-18T00:00:00ZWhat the public AI rules actually say about calculus, where the AP exam still pays for handwork, five classroom uses that keep the reasoning with the student, and three traps that quietly take it away.Calc21https://calc21.com/fundamental-theorem-of-calculusThe Fundamental Theorem of Calculus, in two sentences2026-10-17T00:00:00Z2026-10-17T00:00:00ZThe Fundamental Theorem of Calculus in plain language: what each half says, why it is called fundamental, one worked example where the answer is negative, and the four places a class slips.Calc21https://calc21.com/maria-agnesiWho was Maria Gaetana Agnesi to calculus teachers?2026-10-16T00:00:00Z2026-10-16T00:00:00ZAgnesi wrote the calculus textbook that carried the subject across eighteenth-century Europe, in Italian, for young people. The mistranslation that named the curve after her, and what a classroom can still borrow from the book.Calc21https://calc21.com/calculus-in-the-real-worldCalculus in the real world: five problems where it does the work2026-10-16T00:00:00Z2026-10-16T00:00:00ZFive places calculus is the working tool rather than the exercise: NASA's rocket equation, radiocarbon decay, radar tracking, packaging cost and the method your calculator uses to solve equations. Each one sourced.Calc21https://calc21.com/free-calculus-toolsFree calculus tools: a tour by the job you need done2026-10-14T00:00:00Z2026-10-14T00:00:00ZSixteen free tools for calculus teachers and students — graphing, checking an answer, practising and explained — each described in the vendor's own words.Calc21https://calc21.com/handwritten-frqsHandwritten FRQs in a digital world: practical tips2026-10-13T00:00:00Z2026-10-13T00:00:00ZAP Calculus is a hybrid digital exam: the questions are viewed in Bluebook and the free-response answers are handwritten in paper booklets. What College Board has published about how it works, and the habits that follow.Calc21https://calc21.com/five-calculus-misconceptionsFive calculus ideas students keep mixing up2026-10-11T00:00:00Z2026-10-11T00:00:00ZA limit is not the value of the function, continuous is not differentiable, the Mean Value Theorem is not Rolle's: five distinctions the shorthand drops, with a citable source and a one-sentence fix for each.Calc21https://calc21.com/new-to-calculusTeaching AP Calculus for the first time: the two-minute guide2026-10-10T00:00:00Z2026-10-10T00:00:00ZHanded AP Calculus AB or BC for the first time? The one document to read first, the six steps College Board itself recommends, and where the free material lives.Calc21https://calc21.com/desmos-on-bluebookDesmos on Bluebook: what students can and cannot use2026-10-08T00:00:00Z2026-10-08T00:00:00ZCollege Board's calculator policy for AP Calculus: the Desmos built-in calculator in Bluebook is available only in the calculator-required parts of the exam. Here is exactly where.Calc21https://calc21.com/ap-calculus-2027-changesWhat actually changes in the AP Calculus exam in 20272026-10-08T00:00:00Z2026-10-08T00:00:00ZThe AP Calculus AB and BC syllabus is unchanged, but the exam's multiple-choice count and timing change from May 2027. What College Board has published, and what it has not.Calc21