 
 
 
tchebyshev1 takes as argument an integer n and optionnally a 
variable name (by default x).
tchebyshev1 returns the Tchebychev polynomial of first kind
of degree n.
The Tchebychev polynomial of first kind T(n,x) is defined by
| T(n,x)= cos(n.arccos(x)) | 
and verify the recurrence relation:
| T(0,x)=1, T(1,x)=x, T(n,x)=2xT(n−1,x)−T(n−2,x) | 
The polynomials T(n,x) are orthogonal for the scalar product
| <f,g>= | ∫ | 
 | 
 | dx | 
Input :
Output :
^4+-8*x^2+1Input :
Output :
^4+-8*y^2+1Indeed
| 
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