%% Cotangent of angles approaching 90 and 180 degrees
% Create a vector of input angles consisting of 90° and the next smaller and larger double precision numbers. Then compute the cotangent.

x1 = [90-eps(90) 90 90+eps(90)];
y1 = cotd(x1)

% cotd returns zero when the input angle is exactly 90°. Evaluation at the next smaller double-precision angle returns a slightly positive result. Likewise, the cotangent is slightly negative when the input angle is the next double-precision number larger than 90.
%
% The behavior is similar for input angles near 180°.

x2 = [180-eps(180) 180 180+eps(180)];
y2 = cotd(x2)

% Copyright 2012 The MathWorks, Inc.