Trig algorithms on HP RPN?

[Albert Chan]

(12-01-2024 05:17 PM)Gerson W. Barbosa Wrote:  For example, arctan(0.00001) ~ ln (1.00001). That’s the fifth element in the arctangent table starting at register 1, generated by the HP-15C program B below, when in RAD mode. Program A computes tan(x) using the CORDIC algorithm.

Can you explain in words (better, example) how tan and log1p is used to get atan?