Calling all HP-65 Owners and Lovers


Guys and Gals,

I have a question that I need help with. The HP-65 destroys the contents of Storage Register 9 when performing the following functions: sin, sin-1, cos, cos-1, tan, tan-1, R->P, P->R, x<>y, x<=y, x=y, and x>y.

I have been able to determine what it places there for the sin (the tan(X-Register)), cos (the reciprocal of the tan(X-Register)), R->P (Y-Register squared), P->R (the tan(Y-Register)), and the relational tests all deposit the original value of the X-Register in Storage Register 9.

However, I have been unable to decipher what the sin-1, cos-1, tan, and tan-1 put there. As close as I can tell it has something to do with the inverted squared root of indefinite multiples of a complex random number (just kidding). I have tried plotting values versus results but have had no luck making sense of it.

If anyone out there can tell me what these four functions deposit into Storage Register 9 I would really appreciate it. Any takers?

Matt Riehl

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