Generator

degree

A generator in the computation library, called 22 times across 6 essays. Below: what it draws at its defaults and at each mode an essay asks for, what it checks while drawing, and everywhere it is used.

degree is one function. Everything below came out of it during this build, at parameters taken from the essays rather than invented for this page — so a figure here is the same figure a reader meets in an essay, and if the generator changes, this page changes with it.

At its defaults

The tower ℚ ⊂ ℚ(√2) ⊂ ℚ(√2, √3)A tower of field extensions with the degree of each step, beside the multiplication table of the basis.dim 12ℚ(√2)dim 22ℚ(√2, √3)dim 41√2√3√61√2√3√61√2√3√6√22√62√3√3√633√2√62√33√262 square roots taken, one at a time, and the degree doubles at each: 1 → 2 → 4the 4×4 table is the closure check — every product of basis elements landed on a whole-numbermultiple of another

show: "roots"

Every rational number that could be a root of x² − 2A table of the candidate rational roots allowed by the rational root theorem, with the polynomial's exact value at each.x² − 2candidatevalue thereroot?-22-1-11-122x² − 2 has no rational root — all 4 candidates the theorem allows weretested and none is zerothe numerator of any rational root divides the constant term and thedenominator divides the leading one
Looking for a polynomial with π as a rootA table of the closest an integer polynomial of each degree comes to vanishing at the number, over a bounded search.π = 3.141592654…coefficients from −5 to 5degreeclosest missvalue there1−x + 30.142110 tried2−2x² + 5x + 40.03121,210 tried3−x³ + 2x² + 2x + 50.016113,310 tried4−2x⁴ + 5x³ + 5x² − 4x + 30.00515146,410 tried161,040 integer polynomials of degree ≤ 4 with coefficients in [−5, 5], evaluated at π —none is zerothe same search finds x² − 2 for √2, so its silence about π is a report and not a proof

What it checks while it draws

Collected by running the family and recording what it asserted, not written here. The count is how many separate times the claim was put to the test while these drawings were made.

Where it is called

Changing this generator changes every figure on this list. That is what makes the list worth publishing rather than keeping in a check script.

Computation

Every step is a square root

A line meets a line by solving a linear equation and a circle by solving a quadratic one. There is no third case, so the numbers a construction reaches can only ever double in complexity — and a doubling is a thing that can be counted.

Computation

The angle that will not divide by three

Halving an angle costs one circle. Cutting it in three means solving a cubic, and for sixty degrees that cubic has no rational root — but plenty of angles do trisect, and which ones is a question with a countable answer.

Computation

The circle that will not square

The other three impossibilities are a number having the wrong degree. This one is a number having no degree at all — and that is a claim no finite search can establish, which makes it the one place in this field where the picture has to admit what it is not doing.

Computation

The cube that will not double

Doubling a cube needs an edge in the ratio of the cube root of two. That number satisfies an equation of degree three, three does not divide any power of two, and the oldest open problem in geometry closes in a line.

Computation

What two points can build

A compass and a straightedge are not a craft. They are two operations on a set of points, applied over and over, and writing them that way turns "can this be drawn?" into a question with an answer.

Computation

Which polygons can be drawn

Three sides yes, seven no, seventeen yes. The list of constructible regular polygons is neither everything nor almost nothing, and the pattern in it is a fact about which numbers are one less than a power of two.

The whole library · What the figures prove