Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Why are second kind Chebyshev points the first kind extrema? #174

Open
MikaelSlevinsky opened this issue May 12, 2022 · 0 comments
Open

Comments

@MikaelSlevinsky
Copy link
Member

julia> n = 10
10

julia> pts = chebyshevpoints(Float64, n+1, Val(2))
11-element FastTransforms.ChebyshevGrid{2, Float64}:
  1.0
  0.9510565162951536
  0.8090169943749475
  0.5877852522924731
  0.30901699437494745
  0.0
 -0.30901699437494745
 -0.5877852522924731
 -0.8090169943749475
 -0.9510565162951536
 -1.0

julia> cos.(n.*acos.(pts))
11-element Vector{Float64}:
  1.0
 -1.0
  1.0
 -1.0
  1.0
 -1.0
  1.0
 -1.0
  1.0
 -1.0
  1.0

Shouldn't they be the roots of the second kind Chebyshev polynomials?

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
None yet
Projects
None yet
Development

No branches or pull requests

1 participant