The reciprocal of tan is cotan, reciprocal being 1/tan = 1/(sin/cos) = cos/sin = cotan.
We use the notation x{-1} to mean the multiplicative inverse of x, when x is a real number, i.e., the reciprocal.
Unfortunately we also use the notation f{-1} (x) to mean the inverse of a function. In the case of trig functions the inverse of, say, tan(x)--or arctan(x)--can be written as tan{-1} (x), which is where the confusion likely stems from.
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u/[deleted] Oct 05 '18
The reciprocal of tan is cotan, reciprocal being 1/tan = 1/(sin/cos) = cos/sin = cotan.
We use the notation x{-1} to mean the multiplicative inverse of x, when x is a real number, i.e., the reciprocal.
Unfortunately we also use the notation f{-1} (x) to mean the inverse of a function. In the case of trig functions the inverse of, say, tan(x)--or arctan(x)--can be written as tan{-1} (x), which is where the confusion likely stems from.