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This is the fourth page of my explanation of how to use an RPN
calculator. If you didn't read the first three pages, you might want to
start with the first page.
| Remember, the way that you do arithmetic on an RPN calculator is
- key in the first value
- press the <Enter> key
- key in the second value
- press the appropriate operator key
.
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On this page we're going to use the exponent key (y^x) and
nested calculations to calculate complex roots of numbers.
Calculating complex roots
On the previous page, we used the exponent key to
find a square root. Square roots are easy, because we know the decimal
equivalent of one-half, and it's easy to key that into the calculator. But
what if I asked you for the seventh root of four.
Well, that would be 4 raised to the power of 1/7. You could calculate
1/7 first and write that number down somewhere. Then you would
key in a four, the enter key, the number that you wrote down, and then hit
the exponent key. But there's an easier and more accurate way that doesn't
require you to remember the decimal equivalent of one-seventh.
The other way uses the stack, that we learned about on the
first page of this tutorial, to keep track of things
for us, so we won't have to write anything down. This is what we call a
nested calculation. What we want to calculate is
4^(1/7).
When you want to do this on an RPN calculator, the rules to use are
- Key in numbers from left to right, separating values with the Enter key,
then
- key in the operators from the right to the left.
(This rule works for any series of nested calculations as long as the division
and/or subtraction operators appear only as the rightmost operator.)
To solve 4^(1/7)
| You tap: |
4 | Enter | 1 | Enter | 7 | / | y^x |
An RPN calculator uses its internal stack to perform nested calculations.
Remember that when you press the Enter key several things happen: 1) The
current content of the X register (that's the number in the display)
is moved to the Y register (the top of the stack) and all other numbers
in the stack move down to make room; 2) The X register is cleared to
be ready to accept the next number that you will key into the calculator. The
stack works like those spring-loaded things that dispense plates at the
cafeteria. The stack of the free calculator can
hold up to 20 numbers. That's enough to handle some very complex calculations.
The free calculator has two more buttons on its
keyboard that I haven't mentioned yet. So, we'll cover those
next.
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