@stevework/triangle-completion-sas

triangle-completion

Calc a triangle from a partial spec. Basic trig nicely packaged.

Usage

import { solveTriangle, TriangleError } from 'trig';
console.log(solveTriangle({ alpha:60, beta: 30, B: 1 }));
{
  alpha: 60,
  beta: 30,
  gamma: 90,
  A: 1.7320508075688774,
  B: 1
  C: 2.0000000000000004,
}
console.log(solveTriangle({ A:1, C:2, alpha: 10 }));
{
  A: 1,
  B: 2.907370933399707
  C: 3.7264028721887454,
  alpha: 10,
  beta: 30.32203701650613,
  gamma: 139.67796298349387,
  alt: {
    A: 1,
    B: 2,
    C: 2.907370933399707,
    alpha: 10,
    beta: 20.32203701650614
    gamma: 149.67796298349387,
  },
}

Specifications use alpha, beta, gamma for angles and A, B, C for the corresponding opposite sides. As shown, an SSA spec involving an obtuse angle generates both possible solutions.

Invalid inputs (zero/NaN/undefined, or unsolvable specifications) throw TriangleError, trivially derived from Error. null inputs propogate to the output without throwing an error.

Optimizing

solveTriangle analyzes and mutates the input spec to match up with one of several solver functions. You can call these solver functions directly, saving both the cost of the analysis (for sure a few conditional evaluations and likely a few rotate/invert object manipulations) and the cost in time and space of importing unused logic. The individual solvers are named for the inputs they expect, and packaged into submodules named for the shape of the specification, as follows:

• triangle-completion-aas: Angle-Angle-Side, solve_gamma_alpha_c({ gamma: 20, alpha: 80, C: 3 })
• triangle-completion-asa: Angle-Side-Angle, solve_alpha_b_gamma({ alpha: 80, B: 3, gamma: 20 })
• triangle-completion-sas: Side-Angle-Side, solve_a_gamma_b({ A: 1, gamma: 20, B: 3 })
• triangle-completion-ssa: Side-Side-Angle, solve_a_b_alpha({ A: 1, B: 3, alpha: 40 })
• triangle-completion-sss: Side-Side-Side, solve_a_b_c({ A: 1, B: 3, C: 5 })

There are also some trivial support functions in triangle-completion-common, but it's unlikely they'll be of interest on their own.

Contributing

Zero optimization of code for performance, have at it: [https://github.com/swork/triangle-completion.git]

npx test runs a Jasmine suite, please extend it to reflect your changes.