HP Prime Graphing Wireless Calculator - Manual (Page 218)

214 Functions and commands
5. Tap .
You can run your function by entering it on the entry line
in Home view, or be selecting it from the USER menu. You
enter the value for each variable you chose to be a
parameter. In this example. we chose A and B to be
parameters. Thus you might enter SINCOS(0.5, 0.75).
With C=0 and in radians mode, this would return
1.211…