Cotangent of argument in degrees
Y = cotd(X)
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)
y1 = 1.0e-15 * 0.2480 0 -0.2480
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)
y2 = 1.0e+15 * -2.0159 -Inf 2.0159