Inverse trigonometric functions are the inverse of the usual sine, cosine, and tangent functions, and they can be written two ways. Learn more about inverse trigonometric functions, including their notation, limited range, and how they appear on a graph. ...
But the cosine is always positive on that interval. Therefore cos(Arctan x) always yields a positive result. Remember also from equation 22 that cos(−A) = cos A. To ensure this, use the absolute value sign, and the true final answer iscos(Arctan(1/x)) = | x |/√1+x² ...