HP-35 style trig functions

[Thomas Klemm]

(01-13-2019 08:32 PM)Druzyek Wrote:  Is there another algorithm you can use to find just sine or just cosine that doesn't require square root and multiply?

You may have a look at the Python examples in the attachment of Exploring the CORDIC algorithm with the WP-34S.

You can rotate by an angle and pre-calculate the radius K:

Code:

P, d = 1.0, 1.0
for i in range(N):
    P *= (1 + d*d)
    d /= 2

K = sqrt(P)

This value is a constant depending only on N.

Thus you can use (1/K, 0) as a starting value to calculate the values of cos(arg) and sin(arg) directly:

Code:

# Trigonometrics
arg = 0.4
cordic(0, 1, 1/K, 0, arg, 1.0, ATAN)
# (0.9210609940028851, 0.3894183423086506, -9.860820082244643e-20)
# cos(arg) = 0.9210609940028851
# sin(arg) = 0.3894183423086506

Kind regards
Thomas