Article View: uk.education.maths
Article #149A point and its position vector, your comment please
From: ma
Date: Fri, 27 Mar 1998 00:00
Date: Fri, 27 Mar 1998 00:00
87 lines
4040 bytes
4040 bytes
Assume that a coordinate system of xyz-axes has been chosen. Then both a point P and its position vector \uparrow(OP) are represented by the same triple (a,b,c). Hence we are allowed to write P=(a,b,c)=\uparrow(OP), i.e. P=\uparrow(OP). With this simple notation, we have the simple formula: \uparrow(AB)=B-A. Question: DO you accept or reject the notation P=\uparrow(OP)? The advantage of identifying a point and its position vector can be seen from some formulas such as (a) point-normal form of the plane through A with normal N, (P-A).N=0 (b) mid-point of A,B is (A+B)/2 (c) \uparrow(AB)x\uparrow(AC)=(B-A)x(C-A) (d) point-direction form of a line, P=A+t D, t is real. Otherwise we have to write (\uparrow(OP)-\uparrow(OA) ).N=0 (\uparrow(OA)+\uparrow(OB))/2 \uparrow(AB)x\uparrow(AC) =(\uparrow(OC)-\uparrow(OA))x(\uparrow(OC)-\uparrow(OA)) \uparrow(OP)=\uparrow(OA)+t D, but you still fail to express the point P. =================================================== We all know that a point in the plane is an ordered pair (x,y) and a point in the space that is on xy-plane is an ordered triple (x,y,0). Everybody knows that (x,y)<>(x,y,0) and yet we all accept that the xy-plane is a subset of xyz-space and therefore we are allowed to identify (x,y)=(x,y,0) as long as there is no misunderstanding. =================================================== We all know that the real numbers and complex plane are constructed in completely different way, but we are happy to accept that real field is a subset of the complex field. We accept that the completion K of a uniform space X or a metric space is completely different from X itself but we are happy to accept X as a dense subset of K. There are so many examples that whenever two objects are isomorphic, we do not want to distinguish them. Why should we be so cynical to reject the identification of a point and its position vector whenever a coordinate system HAS been chosen which is the case for high-schools and first-year universities. Same question again: DO you accept or reject the notation P=\uparrow(OP)? Next question: Should we or should we not persuade the textbook writers to adopt the notation P=\uparrow(OP)? Final Question: Does it reflect the psychological insecurity of the older teaching staff in power and in position to accept something is logically correct, conceptually correct and mathematically correct but has an unpopular notation. The bureaucrats want to simplify their forms. Why do the technocrats want to insist on complication?? Is there any standardization organization that I can take this case to them? I DO need your public opinion URGENTLY. Please cast you vote, one way or another. Thank you in advance. Thank you for supporting the global democracy of mathematical education. Your opinion will be copied to a certain web-site and will be available to the global public community. If you want to insist on your own copyright and do not want your opinion to be recorded, please indicate in your posting. Dr. MA, Math Dept, UWA -------------------------------------------------------------------- -- ====================== A new Teaching Worldwide More Acceptable Language is proposed. For further information, please check out the following http://maths.uwa.edu.au/~ma/twma/hello.htm ======================
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X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f458d,333e3e48a480a9d8,start X-Google-Attributes: gidf458d,public X-Google-Thread: 103aae,333e3e48a480a9d8,start X-Google-Attributes: gid103aae,public X-Google-Thread: 1065a2,333e3e48a480a9d8,start X-Google-Attributes: gid1065a2,public From: ma@maths.uwa.edu.au (ma) Subject: A point and its position vector, your comment please Date: 1998/03/27 Message-ID: <ma-2703981552050001@mac89.maths.uwa.edu.au> X-Deja-AN: 338202255 Organization: The University of Western Australia Newsgroups: uk.education.maths,,k12.education.math,,fj.education.math