function p = tch(C,n,x,a,b)
% p = tch(C,n,x)
% p = tch(C,n,x,a,b)
% C is the coefficient list, input.
% n is the degree, input.
% x are the value(s), input.
% a is the left endpoint, input.
% b is the right endpoint, input.
% p are the function value(s), output.
if nargin==3, a=-1; b=1; end
x = 2*(x-a)/(b-a) - 1;
T0 = ones(1,length(x));
p = C(1)*T0;
if n==0, return, end
T1 = x;
p = p + C(2)*T1;
if n==1, return, end
for j=3:n+1,
Tj = 2*x.*T1 - T0;
p = p + C(j)*Tj;
T0 = T1;
T1 = Tj;
end