Rockwell Automation GMLC Reference Manual - Manual (Page 678)

Publication GMLC-5.2 - November 1999
641
The argument can be any floating point value or expression, but it must
have a value from -1 to 1, inclusive, because the cosine of an angle is
always within this range. The value of the Arc_cosine function is always
an angle from 0 to
π
radians (180
°
), inclusive. If the argument is not
between ±1, the value of the Arc_cosine function is zero.
For example, the following expression is evaluated as 1.047xx since the
principal angle whose cosine is 0.5 is 1.047 radians (60
°
).
Arc_cosine(0.5)
To convert the value of the Arc_cosine function to degrees, multiply by
180 /
π
. For example, the following expression is evaluated as 60 (assuming
the user constant Pi has been defined as the value of
π
) since the
principal angle whose cosine is 0.5 is 60
°
.
(Arc_cosine(0.5) * 180 / Pi)
Arc Sine
The value of the Arc_sine function is the principal angle (in radians)
whose sine is equal to the argument, as shown below.
Argument –1
+
–
+1
π