6.13.1 `dacos', `dasin', `datan', `dcos', `dsin', `dtan'
--------------------------------------------------------

dacos(NUM)
     :: Get the value of Arccos of NUM.

dasin(NUM)
     :: Get the value of Arcsin of NUM.

datan(NUM)
     :: Get the value of Arctan of NUM.

dcos(NUM)
     :: Get the value of cos of NUM.

dsin(NUM)
     :: Get the value of sin of NUM.

dtan(NUM)
     :: Get the value of tan of NUM.

RETURN
     floating point number

NUM
     number

   * Compute numerical values of trigonometric functions.

   * These functions use the standard mathematical library of C
     language.  So results depend on operating systems and a C
     compilers.

     [0] 4*datan(1);
     3.14159

