11.4.4 Chebyshev polynomials of the first kind
The Chebyshev polynomial of first kind T(n,x) is defined by
and satisfy the recurrence relation:
T(0,x)=1, T(1,x)=x, T(n,x)=2xT(n−1,x)−T(n−2,x).
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The polynomials T(n,x) are orthogonal for the scalar product
The tchebyshev1
command finds the Chebyshev polynomials of
the first kind.
-
tchebyshev1 takes one mandatory argument and one
optional argument:
-
n, an integer.
- Optionally x, a variable name (by default x).
- tchebyshev1(n ⟨,x⟩) returns
the Chebyshev polynomial of first kind of degree n.
Examples
Indeed, cos(4x)=Re((cosx+i sinx)4)=cos4 x−6cos2 x (1−cos2 x)+((1−cos2 x))2=T(4,cos(x)).