Here's a sample program:
#include<math.h>
main() {
printf("atan2( 0, 1) = %9.6f\\n", atan2( 0., 1.));
printf("atan2( 1, 0) = %9.6f\\n", atan2( 1., 0.));
printf("atan2( 0,-1) = %9.6f\\n", atan2( 0.,-1.));
printf("atan2(-1, 0) = %9.6f\\n", atan2(-1., 0.));
}
This program returns:
atan2( 0, 1) = 0.000000
atan2( 1, 0) = 1.570796
atan2( 0,-1) = 0.000000
atan2(-1, 0) = -1.570796
The result SHOULD be:
atan2( 0, 1) = 0.000000
atan2( 1, 0) = 1.570796
atan2( 0,-1) = 3.141593
atan2(-1, 0) = -1.570796
This anomaly affects the conversion of rectangular-to-polar coordinates, a common use of the atan2 function.
Article Change History:
20 Sep 1994 - Reviewed.
27 Aug 1992 - UPDATED to include A/UX 3.0 Information.
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