equilateral.ts

import type { FnU2 } from "@thi.ng/api";
import { THIRD_PI } from "@thi.ng/math";
import {
    maddN2,
    mag,
    normalize,
    perpendicularCCW,
    sub2,
    Vec,
} from "@thi.ng/vectors";

export const equilateralTriangle2: FnU2<Vec, Vec[]> = (a, b) => {
    const dir = sub2([], b, a);
    const c = normalize(
        null,
        perpendicularCCW([], dir),
        mag(dir) * Math.sin(THIRD_PI)
    );
    return [a, b, maddN2(null, dir, 0.5, c)];
};