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backend_lastx.txt
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backend_lastx.txt
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1. Reusing a number in a calculation.
Suppose we want to compute `sin(6.24) * tan(6.24/2)`
by pressing `6.24 SIN 6.24 2 / TAN *`
6.24 was written to LASTX when pressing SIN so it
can be reused in the following way:
`6.24 SIN LASTX 2 / TAN *`
2. Correcting errors.
2a) Single-argument functions
Suppose we typed `6.24 SIN 6.24 2 / COS` instead
of `6.24 SIN 6.24 2 / TAN`. We can correct it w/o
erasing the whole thing. Before pressing COS,
LASTX will store `6.24/2` so to correct it use:
RDN (get rid of cos(6.24/2)) X -> g sin(6.24))
LASTX (insert LASTX 6.24/2) . .X -> 6.24/2
Y -> sin(6.24)
TAN . . . . . . . . . . . . . .X -> tan(6.24/2)
Y -> sin(6.24)
* X -> sin(6.24) * tan(6.24/2) = 0.00093
2b) 2-argument function and wrong function
Suppose we want to calculate `20*23 (20 ENT 23 *)`
but typed `20 ENT 23 -`. Correct it as follows:
20 ENT 23 - . . . . . . . . . X -> 20 - 23
LASTX . . . . . . . . . . . . X -> 23
Y -> 20 - 23
+ (undo last operation) . . . X -> 20
23 . . . . . . . . . . . . . .X -> 23
Y -> 20
* . . . . . . . . . . . . . . X -> 460
2c) Wrong first number (Y register)
19 ENT 23 * . . . . . . . . . X -> 440
20 . . . . . . . . . . . . . .X -> 20
Y -> 440
LASTX. . . . . . . . . . . . X -> 23
Y -> 20
Z -> 440
* . . . . . . . . . . . . . . X -> 460
Y -> 440
Before starting, we can optionally RND to discard 440.
2d) Wrong second number (X register)
20 ENT 22 * . . . . . . . . . X -> 22 * 20
LASTX . . . . . . . . . . . . X -> 22
Y -> 22 * 20
/ . . . . . . . . . . . . . . X -> 20
23 . . . . . . . . . . . . . .X -> 23
Y -> 20
* . . . . . . . . . . . . . . X -> 23 * 20