but are defined for all real values. (The tangent function is undefined for values of the argument which are odd integer multiples of 
) [M1.6]
are: functions which are equivalent to the trigonometric ratios (sine, cosine, tangent) for arguments in the range 0 to but are defined for all real values. (The tangent function is undefined for values of the argument which are odd integer multiples of ) [M1.6]
often are taken: to include the reciprocal trigonometric functions (cosecant, secant, cotangent). (The cotangent function is undefined for values of the argument which are even integer multiples of ) [M1.6]
are all: periodic functions. [M1.6]
strictly consist; of two distinct classes of functions, those whose domain is the set of real numbers, and those whose domain is the set of angles, but this distinction is deliberately blurred by measuring angles in radians to ensure that the periodicity is the same (apart from the dimensionless unit radian) in both cases.
See trigonometric functions in the Maths handbook for further details.
Copyright 1997, The Open University