I’d Google “forth trig functions” and get, for example https://web.stanford.edu/~dljaffe/SVFIG99/trig.html https://web.stanford.edu/~dljaffe/SVFIG99/trig.html

I’d Google “forth trig functions” and get, for example https://web.stanford.edu/~dljaffe/SVFIG99/trig.html https://web.stanford.edu/~dljaffe/SVFIG99/trig.html https://www.hpmuseum.org/forum/thread-18123.html https://www.hpmuseum.org/forum/thread-18123.html (which links to https://archive.org/details/Forth_Dimension_Volume_04_Number_1/page/n8/mode/1up https://archive.org/details/Forth_Dimension_Volume_04_Number...)