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Topic: improvement on sin(x) = −0.4176x^2 +1.3122x -
0.0504 ;; we need semicircle sine, not the fakery of sinusoi
d sine

Replies: 15   Last Post: Feb 25, 2017 3:31 AM

 Messages: [ Previous | Next ]
 Wally W. Posts: 283 Registered: 6/15/11
Re: probably need to go to a 3rd power polynomial
Posted: Feb 20, 2017 2:59 AM

On Sun, 19 Feb 2017 22:42:59 -0800 (PST), Archimedes Plutonium wrote:

>Alright, at bare minimum I need to get this table:
>
>x y
>0 0
>.5 .86
>1 1
>1.5 .86
>2 0
>
>Now I can come reasonably close by .1 or less, but if more than .1, the game is off
>
>So far, the best two equations for sine and cosine are these two
>
>-.4x^2 + 1.6x + .09
>
>-.6x^2 - .3x +1
>
>Troubles: the first gives 0 as .09, then gives .8 which is good, but gives 1.3 when I need 1. The second gives 1 at 0, good, then .7 when I need .86, then .1 when I need 0 which is acceptable. So unless I can mend the two to fit better, then I must go to a 3rd power polynomial.
>
>AP

Actually, the best two equations for sine and cosine are these two:
y = sin(x)
y = cos(x)