| Pi Times | o. 0 0 0 | Circle Function | 
| 
o. y yields π times y . 
Thus o. 1 is approximately 3.14159 .
 | 
The function x&o. is even or odd as x is even or 
odd; (-x)&o. is its inverse (that is, y = (-x) o. x o. y 
for y in a significant sub-domain).
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  | 
rfd=: 180 %~ o. NB. Radians from degrees sin=: 1&o. SIN=: sin@rfd (rfd 0 90 180);(sin 0 1.5708);(SIN 0 90) +----------------+---+---+ |0 1.5708 3.14159|0 1|0 1| +----------------+---+---+