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 acute 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 import and invoke 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 as follows:

- Angle-Angle-Side: aas.js solveGammaAlphaC({ gamma: 20, alpha: 80, C: 3 })
- Angle-Side-Angle: asa.js solveAlphaBGamma({ alpha: 80, B: 3, gamma: 20 })
- Side-Angle-Side: sas.js solveAGammaB({ A: 1, gamma: 20, B: 3 })
- Side-Side-Side: sss.js solveABC({ A: 1, B: 3, C: 5 })
- Side-Side-Angle: ssa.js solveABAlpha({ A: 1, B: 3, alpha: 40 })

This last is ambiguous if the angle is acute. As shown above, the solution
includes an "alt" key giving another matching triangle. Nothing determines which
solution is presented as "alt".

There are also some trivial support functions in common.js, but it's unlikely
they'll be of much 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.