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elica85

  • 2 years ago

matrix multiplication

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  1. elica85
    • 2 years ago
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    comp being slow, pls wait..

  2. mathsmind
    • 2 years ago
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    ok what is the matrix problem

  3. elica85
    • 2 years ago
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    let x be an arbitrary angle and C represents cosine, S represent Sine

  4. mathsmind
    • 2 years ago
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    and what are the dimensions of those matrices

  5. elica85
    • 2 years ago
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    matrix A= CX -SX 0 aCX SX CX 0 aSX 0 0 1 0 0 0 0 1 matrix B= CY -SY 0 bCY SY CY 0 bSY 0 0 1 0 0 0 0 1

  6. elica85
    • 2 years ago
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    and Y another arbitrary angle..

  7. elica85
    • 2 years ago
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    4x4 matrix

  8. elica85
    • 2 years ago
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    i think i get how to do the multiplication but since there are variables, i'm coming up with crazy figures for each new element in the new matrix. and this new matrix has to be multiplied by another 4x4

  9. mathsmind
    • 2 years ago
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    ok

  10. elica85
    • 2 years ago
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    i guess my problem is more towards trig...is there a simple expressions for each element?

  11. mathsmind
    • 2 years ago
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    i will solve for u as soon as i am done with the other student

  12. elica85
    • 2 years ago
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    thx, or you can just tell me if there's no simple expression cuz i can do all the work, it will just look messy

  13. mathsmind
    • 2 years ago
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    4x4 is a messy matrix, so should expect such a mess

  14. elica85
    • 2 years ago
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    ok. or are you familiar with matlab? from what i remember, you have to have values for matlab...

  15. mathsmind
    • 2 years ago
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    do u want to do this with matlab or using normal mathematical methods

  16. elica85
    • 2 years ago
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    it's just part of the actual problem so i don't think working it out by hand is important so if i can do it on matlab, it would be great

  17. elica85
    • 2 years ago
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    or calculator

  18. mathsmind
    • 2 years ago
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    ok i will do it for u with c++ or c sharp

  19. mathsmind
    • 2 years ago
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    so u just want to multiply those two matrices

  20. elica85
    • 2 years ago
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    i'm not familiar with c++ but there is another matrix, i will type it up..

  21. elica85
    • 2 years ago
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    Matrix C= CZ -SZ 0 cCZ SZ CZ 0 cSZ 0 0 1 0 0 0 0 1

  22. elica85
    • 2 years ago
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    and a,b,c are arbitrary constants. so in c++, you can keep the expression with variables?

  23. mathsmind
    • 2 years ago
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    do u want AxBxC

  24. elica85
    • 2 years ago
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    if that means the same thing as AxB=AB ABxC=result 4x4 matrix

  25. mathsmind
    • 2 years ago
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    ok

  26. mathsmind
    • 2 years ago
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    no it does not mean the same thing but i get what u want now

  27. elica85
    • 2 years ago
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    ok thx

  28. mathsmind
    • 2 years ago
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    am sorry of the delay just someone before u sent me a bunch of questions that i need to type the answers

  29. mathsmind
    • 2 years ago
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    so u can do others stuff and i will finish the work for u as soon as possible

  30. elica85
    • 2 years ago
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    that's fine, i will check later

  31. mathsmind
    • 2 years ago
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    sorry for keeping u waiting but i need to know do u want element by element multiplication or linear algebraic product

  32. mathsmind
    • 2 years ago
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    you have to be precise on that so i can give u the right answer

  33. elica85
    • 2 years ago
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    good question, i was actually trying to figure out on google. all the instructor said was to multiply them. what i found on google was this http://easycalculation.com/matrix/learn-matrix-multiplication.php which is what's going to make the result matrix look real messy. the problem is to find the transformation matrix of a mechanical grabber. so it would have multiple joints, point O as fixed, and point P as the position of the grabber. to find the position, find transformation matrices (which i've done) and the post multipy the matrices to get the result matrix. the matrix C was from point O to joint 1, matrix B is from joint 1 to joint 2, and matrix A is from joint 2 to point P

  34. mathsmind
    • 2 years ago
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    HI THERE I KNOW IT TOOK ME A LONG TIME BUT I PROMISED SOMEONE TO FINISH THERE 50 QUESTIONS

  35. mathsmind
    • 2 years ago
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    syms cosx sinx asinx acosx cosy siny bcosy bsiny cosz sinz csinz ccosz syms cosx sinx asinx acosx cosy siny bcosy bsiny cosz sinz csinz ccosz A=[cosx, -sinx,0, acosx;sinx,cosx,0,asinx;0,0,1,0;0,0,0,1]; B=[cosy, -siny,0, bcosy;siny,cosy,0,bsiny;0,0,1,0;0,0,0,1]; %C=[cosz, -sinz,0, ccosz;sinz,cosz,0,csinz;0,0,1,0;0,0,0,1]; %Linear algebraic product of the matrices... M1= A * B * C; M2= A*B; M3= B*C; M4= A*C; %Array arithmetic operations are carried out element by element M1= A * B * C; M2= A*B; M3= B*C; M4= A*C;

  36. mathsmind
    • 2 years ago
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    the result for linear algebraic multiplication for example A x B

  37. mathsmind
    • 2 years ago
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    A = [ cosx, -sinx, 0, acosx] [ sinx, cosx, 0, asinx] [ 0, 0, 1, 0] [ 0, 0, 0, 1]

  38. mathsmind
    • 2 years ago
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    B = [ cosy, -siny, 0, bcosy] [ siny, cosy, 0, bsiny] [ 0, 0, 1, 0] [ 0, 0, 0, 1]

  39. mathsmind
    • 2 years ago
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    A*B ans = [ cosx*cosy - sinx*siny, - cosx*siny - cosy*sinx, 0, acosx + bcosy*cosx - bsiny*sinx] [ cosx*siny + cosy*sinx, cosx*cosy - sinx*siny, 0, asinx + bsiny*cosx + bcosy*sinx] [ 0, 0, 1, 0] [ 0, 0, 0, 1]

  40. mathsmind
    • 2 years ago
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    so this is what u called messy result which seems to be exclusive of your intuitive expectation, however the element by element matrix multiplication would give a result hopefully to your expectation

  41. mathsmind
    • 2 years ago
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    A.*B ans = [ cosx*cosy, sinx*siny, 0, acosx*bcosy] [ sinx*siny, cosx*cosy, 0, asinx*bsiny] [ 0, 0, 1, 0] [ 0, 0, 0, 1]

  42. mathsmind
    • 2 years ago
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    Array arithmetic operations are carried out element by element, and can be used with multidimensional arrays. The period character (.) distinguishes the array operations from the matrix operations.

  43. mathsmind
    • 2 years ago
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    Sorry i was busy but i have to keep all my promises not matter what, so all the best and good luck.

  44. mathsmind
    • 2 years ago
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    Now with this basic method you can do whatever multiplication you want, and in any associative, distributive ... way you want.

  45. elica85
    • 2 years ago
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    thank you, i think i will have to ask which multiplication is needed since i don't know. i would hope it's the easier one though!

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