HP-35S and angle between two segments in the space « Next Oldest | Next Newest »

 ▼ Antonio Maschio (Italy) Senior Member Posts: 416 Threads: 78 Joined: Mar 2006 04-24-2008, 11:07 AM Hi, I have three points in the space, X, Y, Z, each identified with three space coordinates. ```X(x1,y1,z1) Y(x2,y2,z2) Z(x3,y3,z3) ``` Now I have two segments, one from X1 to X2, the other from X2 to X3. How can I quickly get the angle between these segments with my HP-35S and the vectors capabilities? Thanks in advance to anyone answering. -- Antonio ▼ Howard Boardman Junior Member Posts: 30 Threads: 10 Joined: Jul 2007 04-24-2008, 03:58 PM Not sure about vector operations but the easiest way to me seems to be calculating the distance between the points.. giving you a triangle with known side lengths. Then you can calculate internal angles with the law of cosines. This could easily be written into a program. Chuck Senior Member Posts: 320 Threads: 59 Joined: Dec 2006 04-24-2008, 04:51 PM There are a number of ways, but here is one that uses the equation feature and the dot product. Store points X1, X2, and X3, into A, B, and C. In EQN , create: ``` ACOS((A-B)*(C-B)/(ABS(A-B)*ABS(C-B))) ``` and evaluate the EQN. [EDIT] Be careful with the order the points are entered. My equation makes two vectors B to A, and B to C, or the angle ABC. CHUCK Edited: 24 Apr 2008, 5:43 p.m. after one or more responses were posted ▼ Mark Storkamp Member Posts: 83 Threads: 5 Joined: Oct 2007 04-24-2008, 05:16 PM Quote: In EQN , create: ``` ACOS((A-B)*(C-B)/(ABS(A-B)*ABS(C-B))) ``` and evaluate the EQN. Although that generally should work, the following is from the HP-35S Manual: ```Dot Product Function DOT is used to calculate the dot product of two vectors with the same length. Attempting to calculate the dot product of two vectors of different length causes an error message “Invalid Data”. ``` So it might be better to divide each vector by it's absolute value before using the dot product just to be safe. ▼ marais Member Posts: 204 Threads: 20 Joined: Jun 2005 04-24-2008, 05:36 PM Well, if this is so, the HP35 implementation of the dot product is wrong. My 28C does things as it should. The mathematical definition of the dot product limits it by no means to two normalized vectors. A. Chuck Senior Member Posts: 320 Threads: 59 Joined: Dec 2006 04-24-2008, 05:40 PM Invalid Data is when multiplying vectors [1,2,3] and [4,5], which of course can't be done. "Length" in the manual refers to "number of components", not the Norm of the vector (or at least I assumed this.) CHUCK Antonio Maschio (Italy) Senior Member Posts: 416 Threads: 78 Joined: Mar 2006 04-26-2008, 06:52 AM Thanks to anyone. -- Antonio

 Possibly Related Threads... Thread Author Replies Views Last Post Missing LCD segments (48 SX) Matti Övermark 2 789 09-18-2013, 03:50 PM Last Post: Matti Övermark HP-12C: Missing Segments Stefan Ramonat 2 871 06-28-2013, 10:59 AM Last Post: Stefan Ramonat Too wide spaces between segments of emulated WP34S? René Franquinet 3 872 02-22-2013, 11:14 AM Last Post: René Franquinet Default angle mode Eric Smith 71 7,158 12-06-2012, 01:19 AM Last Post: Eddie W. Shore HP50G Max SDcard Storage space?? mr-scorpio 9 1,684 08-22-2012, 09:57 AM Last Post: Bart (UK) OT - Arduino In Space from HP41 Hacker PeterP 3 1,027 06-16-2012, 10:43 PM Last Post: PeterP OT: Space ship Michael Eckstein 18 2,271 04-04-2012, 12:31 PM Last Post: Michael Eckstein LCD repair tip: Missing segments on heat seated ribbon McAllan 7 1,410 03-11-2012, 08:50 PM Last Post: Joerg Woerner missing segments on 20b running 34s db (martinez, ca.) 4 1,001 10-05-2011, 01:27 AM Last Post: Walter B [alpha][space] in WP34S fhub 23 3,274 08-10-2011, 04:21 PM Last Post: Marcus von Cube, Germany

Forum Jump: