A vector is defined as having three dimensions as being represented by an ordered collection of three numbers:   (X, Y, Z).

If you imagine a graph with the   x   and   y   axis being at right angles to each other and having a third,   z   axis coming out of the page, then a triplet of numbers,   (X, Y, Z)   would represent a point in the region,   and a vector from the origin to the point.

Given the vectors:

        A = (a1,  a2,  a3) 
        B = (b1,  b2,  b3) 
        C = (c1,  c2,  c3) 

then the following common vector products are defined:

 The dot product       (a scalar quantity)
  A • B = a1b1   +   a2b2   +   a3b3  
 The cross product       (a vector quantity)
  A x B = (a2b3  -   a3b2,     a3b1   -   a1b3,     a1b2   -   a2b1)  
 The scalar triple product       (a scalar quantity)
  A • (B x C) 
 The vector triple product       (a vector quantity)
  A x (B x C) 


Task

Given the three vectors:

        a = ( 3,    4,    5)
        b = ( 4,    3,    5)
        c = (-5,  -12,  -13)

 Create a named function/subroutine/method to compute the dot product of two vectors.
 Create a function to compute the cross product of two vectors.
 Optionally create a function to compute the scalar triple product of three vectors.
 Optionally create a function to compute the vector triple product of three vectors.
 Compute and display: a • b
 Compute and display: a x b
 Compute and display: a • (b x c), the scalar triple product.
 Compute and display: a x (b x c), the vector triple product.


References

   A starting page on Wolfram MathWorld is   Vector Multiplication .
   Wikipedia   dot product. 
   Wikipedia   cross product. 
   Wikipedia   triple product.


Related tasks

   Dot product
   Quaternion type


 
# Project : Vector products
 
d = list(3)
e = list(3)
a = [3, 4, 5]
b = [4, 3, 5]
c = [-5, -12, -13]
 
see "a . b = " + dot(a,b) + nl
cross(a,b,d)
see "a x b = (" + d[1] + ", " + d[2] + ", " + d[3] + ")" + nl
see "a . (b x c) = " + scalartriple(a,b,c) + nl
vectortriple(a,b,c,d)
 
def dot(a,b)
    sum = 0
    for n=1 to len(a)
        sum = sum + a[n]*b[n]
    next
    return sum
 
func cross(a,b,d)
     d = [a[2]*b[3]-a[3]*b[2], a[3]*b[1]-a[1]*b[3], a[1]*b[2]-a[2]*b[1]]
 
func scalartriple(a,b,c)
     cross(b,c,d)
     return dot(a,d)
 
func vectortriple(a,b,c,d)
     cross(b,c,d)
     cross(a,d,e)
     see "a x (b x c) = (" + e[1] + ", " +e[2] + ", " + e[3] + ")"
 