GE PACSystems RX7i

Chapter 4. Ladder Diagram (LD) Programming
66 PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual GFK-2950C
4.1.4 Inverse Trig – ASIN, ACOS, and ATAN
Mnemonics:
ASIN_REAL
ASIN_LREAL
ACOS_REAL
ACOS_LREAL
ATAN_REAL
ATAN_LREAL
When an Inverse Sine (ASIN), Inverse Cosine (ACOS), or Inverse Tangent (ATAN) function receives
power flow, it respectively computes the inverse sine, inverse cosine or inverse tangent of IN and
stores the result in radians in output Q.
The ASIN and ACOS functions accept a narrow range of input values, where –1 ≤ IN ≤ 1. Given a valid
value for the IN parameter, the ASIN function produces a result Q such that:
2
π
Q
2
π
ASIN(IN) 
The ACOS function produces a result Q such that:
πQ0ACOS(IN) 
The ATAN function accepts the broadest range of input values, where –∞ ≤ IN ≤ +∞. Given a valid
value for the IN parameter, the ATAN function produces a result Q such that:
2
π
Q
2
π
ATAN(IN) 
The power flow output is energized unless one of the following invalid conditions occurs:
■ IN is outside the valid range for ASIN, ACOS, or ATAN
■ IN is a NaN (Not a Number)
Operands of Inverse Trig Functions
Parameter
Description
Allowed Operands
Optional
IN
The REAL or LREAL value to process.
ASIN and ACOS: -1  IN  1
ATAN: –∞ ≤ IN ≤ +∞
All except variables located in %S - %SC
No
Q
Trigonometric value of IN. REAL or
LREAL value expressed in radians.
ASIN: (-/2)  Q  (/2)
ACOS: 0  Q  
ATAN: (-/2)  Q  (/2)
All except constants and variables located in
%S - %SC
No