LimitIntro.mws

>   

Unit 1: Limits

Auxiliary Procedures -- do not display

>    restart;
with( plots ):
with( Student[Calculus1] ):

Warning, the name changecoords has been redefined

>    figure := proc( theta )
  local A, C, P, S, T, Title;
  C := implicitplot( x^2+y^2=1, x=-1..1, y=-1..1, tickmarks=[0,0] ):
  S := theta -> plot( [[0,0],[cos(theta),sin(theta)],[cos(theta),0]], color=blue ):
  A := theta -> plot( [cos(theta)*cos(t),cos(theta)*sin(t),t=0..theta], color=green ):
  P := theta -> pointplot( [ [1,0],
                           [cos(theta),0],
                           [cos(theta)*cos(theta),cos(theta)*sin(theta)],
                           [cos(theta),sin(theta)] ],
                           symbol=circle, symbolsize=12 ):
  T := theta -> textplot( {
                  [-0.1,-0.1,"O"],
                  [1.25,-0.1,"A (1,0)"],
                  [cos(theta),-0.1,"B"],
                  [cos(theta)*cos(theta)-0.1,cos(theta)*sin(theta)+0.1,"C"],
                  [cos(theta)+0.25,sin(theta)+0.1,"P (cos t, sin t)"],
                  [-0.2,1.1,"(0,1)"],
                  [0.3,0.1,"t"] } ):
    Title := proc( theta )
      if nargs > 1
        then
          if args[2]=`shorttitle`
            then return sprintf( "Unit circle with theta=%07.5f", theta )
            else return ""
          end if
        else
          return sprintf( "  When t=%07.5f:\narea( sector(COB) ) =   %07.5f\narea( triangle(POB) ) = %07.5f\narea( sector(POA) ) =   %07.5f",
                            theta,
                            abs(theta)*cos(theta)^2/2,
                            cos(theta)*abs(sin(theta))/2,
                            abs(theta)/2 ):
      end if
    end proc;
  plots[display]( [C,S(theta),A(theta),P(theta),T(theta)],
                  view=[-1.5..1.5,-1.5..1.5],
                  title=Title(args),
                  scaling=constrained ):
end proc:

>   

>    # Epsilon-Delta Maplet
# Copyright 2002 Waterloo Maple Inc.
# This maplet graphically illustrates the delta-epsilon definition of the limit.  The definition states that limit( f(x), x=a ) = L if, for all e>0, there exists d>0 such that 0<|x-a|<d implies |f(x)-L|<e.  
#
# Enter a function f(x) and values for a, L, e and d.  You can then experiment with the values of a, e and d to try and find values that satisfy the definition by seeing the plot of f(x) around x=a annotated with these values.  Note that d satisfies the definition as long as the blue region fits between the two red horizontal lines on the plot.
#
# In the plot, x=a is marked by a gray vertical line, and the value L by a gray horizonal line.
#
# The interval [a-d, a+d] is marked by a blue line on the x-axis.
#
# The range of function values implied by the choice of d is marked by a blue region.
#
# The two red horizontal lines indicate y=L+e and y=fL-e.
#
# To run this maplet, click the !!! button in the tool bar.
#
#restart:
with(LinearAlgebra):
with(plots):
with(plottools):
with(Maplets[Elements]):

############################################################
# the drawing procedure

cgraph :=  proc(f, a, L, ep, deltav, xmin, xmax, ymin, ymax)

  local fc, g, aline, Lline, e, ept1, ept2, elinem, elineu, elinel, asd,
        aad, dptr1, dptr2, dliner, dptb1, dptb2, dlineb, j, k, p1, p2, delta;

  #plotting the graph
  fc := plot(f, x=xmin..xmax, y=ymin..ymax, color=navy);

  #drawing a vertical and horizonal line though (a,f(a))
  g := unapply(f, x):
  aline := line([a, 0], [a, L], thickness=2, color=gray):
  Lline := line([xmin, L], [xmax, L], color=gray):

  #scaling the value from the epsilon-slider to between 0 and 1
  e := ep/100:

  #drawing the epsilon neighborhood and horizonal lines at the epsilon end-points
  ept1 := [0, L-e]:
  ept2 := [0, L+e]:
  elinem := line(ept1, ept2, thickness=4, color=red):
  elineu := line([xmin, L+e], [xmax, L+e], color=red):
  elinel := line([xmin, L-e], [xmax, L-e], color=red):

  #scaling the value from the delta-slider to between 0 and 1
  delta := deltav/100:

  asd := a-delta:
  aad := a+delta:

  #the shaded in parts
  p1 := polygon([[asd, 0], [asd, g(aad)], [aad, g(aad)], [aad, 0]],
                 color=turquoise, style=patchnogrid):
  p2 := polygon([[0, g(aad)], [0, g(asd)], [aad, g(asd)], [aad, g(aad)]],
                 color=turquoise, style=patchnogrid):

  #drawing the vertical lines from a+-delta to the function

  dptr1 := [asd, 0]:
  dptr2 := [aad, 0]:
  dliner := line(dptr1, dptr2, thickness=4, color=blue):
  dptb1 := [0, g(asd)]:
  dptb2 := [0, g(aad)]:


  plots[display](aline, Lline, fc, elinem, elineu, elinel, dliner, p1, p2):

end proc:

############################################################
# converts the value chosen on the slider into the real value
# chosen for epsilon and delta

realvalue := proc(rvalue)
  evalf[3](rvalue/100.0):
end proc:

Warning, the name arrow has been redefined

>    f := 3*sqrt(x)/(x+1):
a := 3:
L := limit( f, x=a ):
plotED := cgraph(f, a, L, 12, 50, 0, 4, 0, 2):
plotL1 := textplot( {[a-0.25,-0.1,"d"], [a+0.25,-0.1,"d"] }, font=[SYMBOL,18], color=blue ):
plotL2 := textplot( {[-0.2,L-0.12,"e"], [-0.2,L+0.12,"e"]}, font=[SYMBOL,18], color=red ):
plotL3 := textplot( {[a,-0.1,"a"], [-0.2,L,"L"]}, font=[TIMES,ITALIC,18] ):
R := display( [plotED, plotL1, plotL2, plotL3], view=[-0.2..5,-0.2..1.7], tickmarks=[4,3], labels=["",""], title=sprintf("An epsilon-delta Graph for\nlimit( %a, x=%a ) = %a", f, a, L) ):

>   

Limits are the foundation for all of calculus. In Unit 2 and Unit 3  we will see a special limit that is the basis for derivatives and differential calculus. Later, in Unit 4 and Unit 5, we will see another useful limit - the definite integral.

[Maple Plot]

  

The eight lessons in this unit are organized to develop an Conceptual Understanding of limits before giving a Precise Definition of the limit. To avoid having to use the definition to evaluate every limit, a collection of Limit Laws are developed. Trigonometric Functions, Limits at Infinity, and Infinite Limits are also discussed. The final topics are Continuity and the Intermediate Value Theorem. Each discussion builds towards the first major application of limits: the derivative.

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