4 ms·
How is a rotation matrix "a trick"? It is just ordinary highschool maths.
by nurettin 9y ago
How is a rotation matrix "a trick"? It is just ordinary highschool maths.
- evincarofautumn 9y agoThe “trick” is decomposing it in terms of only skewing and stretching because those are the operations available in Paint.
- kowdermeister 9y agoProbably in high schools where they teach matrixes at all.
- kuschku 9y agoWhich are on the "REQUIRED" part of the curriculum in German high schools.
- pavel_lishin 9y agoThey certainly weren't in rural Texas, where I went to school.
- kuschku 9y agoI think common core is supposed to include them now, so that school should teach them nowadays.
- tedunangst 9y agoCurriculum changes aren't retroactive.
- dymk 9y agoI dunno about you but my middle school makes me come back every 5 years to go over newly added content. Flying all that way really is a pain.
- a_t48 9y agoMy school (mid 2000s) skipped over them.
- germanier 9y agoThey are not in Germany, see https://www.kmk.org/fileadmin/Dateien/veroeffentlichungen_beschluesse/2012/2012_10_18-Bildungsstandards-Mathe-Abi.pdf https://www.kmk.org/fileadmin/Dateien/veroeffentlichungen_be... which lists it as one optional alternative.
- kuschku 9y agoThe KmK requires as minimum either Vectorial Analytical Geometry, or Linear Transformations (and both of these topics would teach people about this topic). States can add upon these requirements, and several require both.
- germanier 9y agoAs the document clearly states matrix transformations are not part of the core curriculum in both topics[0]. You also know that not every German student goes through this curriculum at all. [0]: Yes, it's just a multiplication which is taught but be honest: How many students will come up with that on their own without being told?
- JosephRedfern 9y agoThis is about achieving rotation through a combination of skewing and scaling about X and Y, not just about a direct application of a rotation matrix. It's a trick because to many it's not immediately obvious (even if you know about transformation matrices). This is exactly the kind of thing I visit HN for -- the demonstration and explanation of an interesting hack. You may not have found it interesting, which is perfectly fine, but please don't assume that others didn't.
- nurettin 9y agoI'm sorry I assumed obvious transformations are obvious for everyone. Won't do it again. Thanks for shaming me. It is an honour. You make very high quality and original comments on HN, I will bookmark this thread and come back to read your awesome content later.
- gugagore 9y agoIt's just that you reduced it to "rotation matrices". And that's not what the trick is. The trick is factoring the rotation matrix into some easier matrices.