Changelog

The course list is split into high school and college, with a heading over each group, so the two college courses no longer read as a continuation of the school sequence. AP Statistics has moved up ahead of the calculus courses: it sat after AP Calculus BC, which made it look like the end of the run rather than the separate track it is. Nobody loses their place — a saved course and a mastery score are both stored by name, not by position in the list.

Added Linear Algebra, the other course that comes after BC: ten units covering systems and row reduction, matrix algebra, determinants, inverses and Cramer's rule, vector spaces and independence, rank and the four subspaces, linear transformations, eigenvalues and eigenvectors, orthogonality and least squares, and diagonalisation. It goes without a calculator throughout, since the calculator will row reduce, invert, take a determinant and fit a least-squares line for you, and those are the course.

Added Multivariable Calculus, the course that comes after BC: nine units covering vectors in space, lines, planes and surfaces, vector-valued functions, partial derivatives, gradients and directional derivatives, optimisation with Lagrange multipliers, double and triple integrals, and line and surface integrals through to Green's and Stokes' theorems. It was asked for by two of the partner schools whose students finish BC in junior year. It is worked by hand throughout, like the rest of the calculus sequence.

Questions that ask for a formula accept the right-hand side on its own. Writing lwh instead of V = lwh was being marked wrong for the missing V, which tested copying rather than the formula.

Loop practice no longer walks a course in unit order. Each pass still covers every unit once, in a different order, so the next question is not the one you could already name. A session saved mid-loop before this change starts its current question again.

Calculator errors read like a calculator's: a function it cannot make sense of now says so in a line, and the graph names the row it could not read rather than explaining itself.

The calculator writes real maths again. The expression box is the same editor the answer box uses, so a fraction looks like a fraction and a matrix looks like a matrix, and the completion list came with it: start typing a name and the ones that match appear with their arguments, Tab takes the highlighted one, and while the caret is inside a call its arguments are shown with the one being typed picked out. The box is taller, because what goes in it is a fraction or a matrix as often as it is a number. Also fixed sin(π) reading 1.2e-16 instead of 0, and the same for cos(90°) and the other angles where the answer is exactly zero.

The calculator is now a graphing calculator, on two screens. Calculate takes one expression that understands everything the courses need: trigonometry and logs to any base, nCr and nPr, the distributions (normalcdf, invnorm, tcdf, invt, chi2cdf, binompdf, binomcdf, geometpdf, poissonpdf), one- and two-variable statistics over a list written in brackets, and determinants, inverses and row reduction over a matrix written the same way. Start typing a name and it offers the ones that match, with their arguments; Tab takes the highlighted one and Enter works the answer out. Graph plots up to three functions, and moving across it reads a point off the curve, settling on zeros, turning points, intercepts and crossings; the arrow keys do the same without a mouse. Scroll to zoom about the pointer, drag with the middle button to move, and double-click to put the window back where it started. The area between two limits is the one thing left with a button, because it is the one thing that cannot be read off the curve.

New questions that the old calculator could not answer. AP Statistics adds a normal proportion, an exact binomial probability, a one-proportion p-value, a one-sample t p-value, and a least-squares slope worked from the data itself — the inference questions no longer have to hand out every critical value. Precalculus unit 10 adds a 3 by 3 determinant, the determinant of a product, and a three-equation system solved from its augmented matrix. A practice set saved before today keeps the questions it was given.

Questions are written the way a student would write them. A rolled coefficient of 1 was reaching the page as "1x + 4 = 6", a negative shift as "y = (x − (0))² + (-1)", and a period as "2π/2"; the worked answer came back as "6 · x²" and "y=4·x+(-1)". Also fixed a proportion whose two sides were the same fraction, a rational function whose numerator was a multiple of its denominator, two graph questions that gave away the coordinates they asked you to read, "a octagon", and "1 study hours".

Removed the reading-time check from the counted-work rule. It refused quick right answers on short questions, which was wrong: a vertical-angles question is answered honestly in a second. Pasting and leaving the page still keep an answer from counting. Also fixed the Check button under a multiple-choice list stretching taller than it should.

Fixed a right answer on a second try, after a wrong one on the same question, counting toward the session goal, streak and mastery. It is still checked and explained, and the feedback now says it did not count.

Calculator permission now follows the tests each course leads to. Algebra 1, Geometry and Algebra 2 allow a calculator by default, as the Tennessee and Georgia end-of-course tests do on all but their opening no-calculator subpart; the by-hand units (order of operations, one-variable equations, exponents, polynomial and rational arithmetic, angle relationships and polygon angles) go without. Precalculus and AP Calculus keep the exam split: no calculator unless the unit is one where the exam calls for it.

Fixed the browser's Back button from a practice set opening the unit picker on the wrong course. The picker now follows the course in the address bar.

A correct answer now counts toward the session goal, streak and mastery only when the question was worked on the page. An answer that is pasted in, arrives before the prompt could have been read, or follows a switch to another window while the question was open is still checked, and the feedback says why it did not count. This is a deterrent measured in the browser, not proof of anything.

Polar graphs. Precalculus unit 7 and AP Calculus BC unit 9 now draw polar curves on a labelled polar grid, with questions on converting coordinates, naming a graph from its equation, tangent slopes, and areas inside and between curves. Answers are exact in π unless the question says to round.

Loop practice now finishes at 20 correct answers per unit in the course, matching the goal for a single unit. It was 40 per unit, which several teachers told us was too long to finish in a period. Each course page also carries a short description of what it covers.

Added an SAT Math practice unit at the end of Algebra 2, by request from partner schools. Mixed question types across the four SAT domains, with a calculator allowed throughout as on the digital test.

Geometry is available to licensed schools: eleven units with labelled diagrams, coordinate and multiple-choice answers, and short proofs answered by choosing a reason for each step. Calculator permission is now set per question instead of per unit.

Fixed timer drift on timed sets. Improved implicit differentiation problem generator.

AP Calculus BC (beta) for partner schools. Unit list matches the current College Board sequence; BC-only units are marked.

Accessibility fixes for screen readers on the answer input. The feedback area is now announced when it changes.

Class overview CSV export includes per-unit mastery. Fixed a rounding error in class averages.

Teachers can assign a set to more than one period at a time. Due dates now respect school time zone.

Corrected three Precalculus trig identity problems that accepted an equivalent form incorrectly. Thanks to the teacher who reported it.