toAffineChart(ZZ,List) -- coordinates of a point in the projective space in an affine chart

Synopsis

Usage:
y = toAffineChart(i,x)
Function: toAffineChart
Inputs:
- i, an integer, the numebr of the standard chart
- x, a list, projective coordinates of a point
Outputs:
- y, a list, coordinates of x in the i-th affine chart

i1 : toAffineChart(2,{1,2,3,4,5,6}) 

      1  2  4  5
o1 = {-, -, -, -, 2}
      3  3  3  3

o1 : List

i2 : toAffineChart(2,{1,2,0,4,5,6}) 

o2 = infinity

o2 : InfiniteNumber

i3 : CC[x,y];

i4 : s = track({x^2-y^2},{x*y},{{1,1}})

o4 = {{3.06193e-17, 1.0001}}

o4 : List

i5 : toAffineChart(0, coordinates s#0)

o5 = {3.26625e16}

o5 : List

i6 : toAffineChart(1, coordinates s#0)

o6 = {3.06162e-17}

o6 : List

Returns infinity if the i-th coordinate of x is zero.