Mathc,
Calculus Packages,
Matrices Packages,
Vectors Packages.
 In these packages, you can verify the result into GnuPlot.                 
Calculus  Packages :
  
Chapter 03 : The Derivative. 
 The tangent :           
c03a.zip.
        
    * Draw    the tangent.
    * Animate the tangent.
    * Find the intersection points of the tangent with the x-y axis.
    * Find the length of the tangent from P to the x axis.
    * Find the length of the tangent from P to the y axis.
    * Find the length of the under tangent.
 The normal :        
c03b.zip.
        
    * Draw    the normal.
    * Animate the normal.
    * Find the intersection points of the normal with the x-y axis.
    * Find the length of the normal from P to the x axis.
    * Find the length of the normal from P to the y axis.
    * Find the length of the under normal.
Matrices Packages :
mtrxgo.zip 
                :  Geometric applications.
                * Find the coefficients of a polynome, 
                  that passes through three, four, five points.    
                * Find the coefficients a, b, c, d, e of a conic,
                  ax**2 + by**2 + cx + dy + e  = 0 
                  that passes through  four points.  
                * Find the coefficients a, b, c, d  of a circle,
                  a(x**2 + y**2) + bx + cy + d  = 0   
                  that passes through  three points. 
Vectors Packages :
vectac01.zip : 
                   * Reflection about the x-axis.
                   * Reflection about the y-axis.
                   * Reflection about the line y = x.
                   * Orthogonal projection on the x-axis. 
                   * Orthogonal projection on the y-axis.
vectad.zip : 
                   * Vector2d  (vertical horizontal shift).
vectae01.zip : 
                   * Reflection about the xy-plan.
                   * Reflection about the xz-plan.
                   * Reflection about the yz-plan.
                   * Orthogonal projection on the xy-plan. 
                   * Orthogonal projection on the xz-plan. 
                   * Orthogonal projection on the yz-plan.