︠43e1c86c-95d0-4907-a8ba-8fe19ed4dbe2i︠
x,y=var('x y')
html('<h2>Explaining approximation of a function in two \
variables by differential</h2>')
html('Points x0 and y0 are values where the exact value of the function \
is known. Deltax and Deltay are displacements of the new point. Exact value \
and approximation by differential at shifted point are compared.')
@interact
def _(func=input_box('sqrt(x^3+y^3)',label="f(x,y)=",type=str), x0=1, y0=2, \
  deltax=slider(-1,1,0.01,0.2),\
  deltay=slider(-1,1,0.01,-0.4), xmin=0, xmax=2, ymin=0, ymax=3):
  f=sage_eval('lambda x,y: ' + func)
  derx(x,y)=diff(f(x,y),x)
  dery(x,y)=diff(f(x,y),y)
  tangent(x,y)=f(x0,y0)+derx(x0,y0)*(x-x0)+dery(x0,y0)*(y-y0)
  A=plot3d(f(x,y),(x,xmin,xmax),(y,ymin,ymax),opacity=0.5)
  B=plot3d(tangent(x,y),(x,xmin,xmax),(y,ymin,ymax),color='red',opacity=0.5)
  C=point3d((x0,y0,f(x0,y0)),rgbcolor='blue',size=9)
  CC=point3d((x0+deltax,y0+deltay,f(x0+deltax,y0+deltay)),rgbcolor='blue',size=9)
  D=point3d((x0+deltax,y0+deltay,tangent(x0+deltax,y0+deltay)),rgbcolor='red',size=9)
  exact_value_ori=f(x0,y0).n(digits=10)
  exact_value=f(x0+deltax,y0+deltay)
  approx_value=tangent(x0+deltax,y0+deltay).n(digits=10)
  abs_error=(abs(exact_value-approx_value))
  html(r'Function $ f(x,y)=%s \approx %s $ '%(latex(f(x,y)),latex(tangent(x,y))))
  html(r' $f %s = %s$'%(latex((x0,y0)),latex(exact_value_ori)))
  html(r'Shifted point $%s$'%latex(((x0+deltax),(y0+deltay))))
  html(r'Value of the function in shifted point is $%s$'%f(x0+deltax,y0+deltay))
  html(r'Value on the tangent plane in shifted point is $%s$'%latex(approx_value))
  html(r'Error is $%s$'%latex(abs_error)) 
  show(A+B+C+CC+D)
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︠b9e8394b-ab61-447b-906c-3eec7075b697︠











Collaborative Calculation and Data Science

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sagemath

Explaining approximation of a function in two variables by differential

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