To be a little bit more clear about what I mean, if you have an equilateral triangle with a hypotenuse of length 10 and angle 27 degrees you could find the coordinates by doing pt = 10 * [cos(27), sin(27)]; But you could also find those points by doing pt = zrot(27, [10,0]); Both produce the same result, but the first one requires explicit trigonometry and the second one is geometric. There are a bunch of trigonometric relations in trigonometry.scad that encode the contents of SOHCAHTOA, as well as the law of sines and the law of cosines, but I think the ideal situation is that you are able to define your model entirely by its geometry, without even having to use those. On Thu, Sep 25, 2025 at 3:59 PM Robert Carlson <lostinthetrees@me.com> wrote: > Excellent, can't tell you how many times I have had to look up one of > those rules in the last year or two. > > -Bob > > On Sep 25, 2025, at 18:37, Adrian Mariano via Discuss < > discuss@lists.openscad.org> wrote: > > There seem to be people who get a kick out of solving trig problems when > building their models. I would rather focus on the geometry when building a > model rather than computational details and I tend to think that one of the > jobs of BOSL2 is to do the trig for you. In some sense in you have to > resort to using trig it is a failure of the library. > > On Thu, Sep 25, 2025 at 11:38 larry via Discuss < > discuss@lists.openscad.org> wrote: > >> On Thu, 2025-09-25 at 14:48 +0100, Roger Whiteley via Discuss wrote: >> > Trig, hmm. >> > >> > There's a mnemonic we were taught which I still remember: >> > >> > SOHCAHTOA >> > >> > or sin (angle) = OPPOSITE/HYPOTENUSE >> > >> > or cos (angle) = ADJACENT/HYPOTENUSE >> > >> > or tan (angle) =OPPOSITE/ADJACENT >> > >> > Remembering the mnemonic is easier, for my grey cells. I've probably >> > used that more since taking up OpenSCAD than in the previous 50+ years, >> > I used it last week, to calculate the length of a line from a 3D object >> > rotated along an axis and projected onto the XY plane. All so I could >> > put holes in right place. >> >> Nice, but there's little chance I could remember it, and even less >> chance I could apply it. >> >> I will never forget how to look it up in BOSL2 or in an online triangle >> calculator. >> >> L >> _______________________________________________ >> OpenSCAD mailing list >> To unsubscribe send an email to discuss-leave@lists.openscad.org > > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org > > >

I meant a right triangle, not equilateral! On Thu, Sep 25, 2025 at 7:02 PM Adrian Mariano <avm4@cornell.edu> wrote: > To be a little bit more clear about what I mean, if you have an > equilateral triangle with a hypotenuse of length 10 and angle 27 degrees > you could find the coordinates by doing > > pt = 10 * [cos(27), sin(27)]; > > But you could also find those points by doing > > pt = zrot(27, [10,0]); > > Both produce the same result, but the first one requires explicit > trigonometry and the second one is geometric. > > There are a bunch of trigonometric relations in trigonometry.scad that > encode the contents of SOHCAHTOA, as well as the law of sines and the law > of cosines, but I think the ideal situation is that you are able to define > your model entirely by its geometry, without even having to use those. > > > On Thu, Sep 25, 2025 at 3:59 PM Robert Carlson <lostinthetrees@me.com> > wrote: > >> Excellent, can't tell you how many times I have had to look up one of >> those rules in the last year or two. >> >> -Bob >> >> On Sep 25, 2025, at 18:37, Adrian Mariano via Discuss < >> discuss@lists.openscad.org> wrote: >> >> There seem to be people who get a kick out of solving trig problems when >> building their models. I would rather focus on the geometry when building a >> model rather than computational details and I tend to think that one of the >> jobs of BOSL2 is to do the trig for you. In some sense in you have to >> resort to using trig it is a failure of the library. >> >> On Thu, Sep 25, 2025 at 11:38 larry via Discuss < >> discuss@lists.openscad.org> wrote: >> >>> On Thu, 2025-09-25 at 14:48 +0100, Roger Whiteley via Discuss wrote: >>> > Trig, hmm. >>> > >>> > There's a mnemonic we were taught which I still remember: >>> > >>> > SOHCAHTOA >>> > >>> > or sin (angle) = OPPOSITE/HYPOTENUSE >>> > >>> > or cos (angle) = ADJACENT/HYPOTENUSE >>> > >>> > or tan (angle) =OPPOSITE/ADJACENT >>> > >>> > Remembering the mnemonic is easier, for my grey cells. I've probably >>> > used that more since taking up OpenSCAD than in the previous 50+ >>> years, >>> > I used it last week, to calculate the length of a line from a 3D >>> object >>> > rotated along an axis and projected onto the XY plane. All so I could >>> > put holes in right place. >>> >>> Nice, but there's little chance I could remember it, and even less >>> chance I could apply it. >>> >>> I will never forget how to look it up in BOSL2 or in an online triangle >>> calculator. >>> >>> L >>> _______________________________________________ >>> OpenSCAD mailing list >>> To unsubscribe send an email to discuss-leave@lists.openscad.org >> >> _______________________________________________ >> OpenSCAD mailing list >> To unsubscribe send an email to discuss-leave@lists.openscad.org >> >> >>