Cubic and Quartic Formulae

[Tim Wessman]

Very interesting! Thanks for the comments.

(08-06-2015 01:42 PM)LCieParagon Wrote:  For instance (if we are talking about degrees), one can find sin(36), sin (18), sin(54), and sin(72) exactly. This angles are incredibly useful for architecture or engineering. One can apply half-angle, addition/subtraction, and double angle formulae to receive every whole number degree divisible by 3.

If I am remembering my math from ages ago correctly, you can always find an exact angle if you go out far enough... how would you decide at which point it is useful to find an exact angle or not? Would something like this be implemented by generating a collection of "interesting" values of finer and finer resolution until you were happy with the capability?


Speaking of the nspire, why would doing something like sin(73) in degrees helpfully convert it to "cos(17)"? Simply moving to a smaller angle in the trig function, or is that a common thing?