Remote Processing BASIC 52 - Manual (Page 23)

RPBASIC-52 PROGRAMMING GUIDE
2-4
ATN
Syntax: A T N (expr)
Where: expr = value betw een 0 and P I/2
Function: Returns a trigon ometric arc-ta ngent of expr. Returned result is between -PI/2 and PI/2 radians.
Mode: Comm and, run
Use: PRINT 4*AT N(1)
Cards: All
D E S C R IP T I ON
SIN, COS, and TAN operators use a Taylor series to calculate the function. These operators first reduce the
argument to a value that is between 0 and PI/2. The algorithm used to reduce the value will reduce accuracy
when expr is large. To maintain accuracy, keep the arguments for trig functions as small as possible.
ERRORS
A R I T H . U N D E R F L O W expr or result is less than RPBASIC-52's smallest floating-point value of ±1E-127
A R I T H . O V E R F L O W expr or result is greater than RPBASIC-52's largest floating-point value of
±.9999999E+127
D I V I DE B Y Z E R O Attempt to take TAN(X) when COS(PI/2) = 0
EXAMPLES
100 PRINT SIN(PI/2),COS(10001*PI),TAN(5*PI/4)
110 PRINT ATN(TAN(PI/4))/PI
>run
1 -1 1
.24999996