Trignometric Functions

  The functions in this group can all be used on real or double precision arguments, and SIN and COS can also be used on complex numbers. In every case the result has the same data type as the argument.

* = SIN(RDX)	sine of the angle in radians.
* = COS(RDX)	cosine of the angle in radians.
* = TAN(RD)	tangent of the angle in radians.
* = ASIN(RD)	arc-sine; the result is in the range $- \pi /2$ to $+\pi /2$.
* = ACOS(RD)	arc-cosine; the result is in the range 0 to $+ \pi$ .
* = ATAN(RD)	arc-tangent; the result is in the range $- \pi /2$ to $+\pi /2$.
* = ATAN2(RD,RD)	arc-tangent of arg1/arg2; the result is in the range $- \pi$ to $+ \pi$. Both arguments must not be zero.
* = SINH(RD)	hyperbolic sine.
* = COSH(RD)	hyperbolic cosine.
* = TANH(RD)	hyperbolic tangent.

Note that the arguments of SIN, COS, and TAN must be angles measured in radians (not degrees). They can be used on angles of any size, positive or negative, but if the magnitude is very large the accuracy of the result will be reduced. Similarly all the inverse trigonometric functions deliver a result in radians; the argument of ASIN and ACOS must be in the range -1 to +1. The ATAN2 function can be useful in resolving a result into the correct quadrant of the circle, thus:
ATAN(0.5) = 0.4636476
ATAN2(2.0,4.0) = 0.4636476
ATAN2(-2.0,-4.0) = -2.677945 ( = 0.4636476 - $\pi$).