How to use "Engineer Notation" (SI Prefixes)?

[rushfan]

On my casio scientific calculator, I can do things like multiplying 5M*1µ to return 5.
When I do the same multiplication in the HP Prime, it returns 5_M*µ.
There should be an easy way to handle SI Prefixes in the CAS.
I've tried using the Prefixes in the Units menu, but I couldn't make it work proper.

The way it work on the casio can be seen here: https://www.youtube.com/watch?v=_1aHyFWdQOs
Here is the multiplication on my casio:


Here is the same multiplication on the HP Prime:

[Joe Horn]

I think that Prime only "understands" SI prefixes when they are attached to valid units, which IMHO makes sense, because they are prefixes, not units.

[rushfan]

(05-16-2017 02:20 AM)Joe Horn Wrote:  I think that Prime only "understands" SI prefixes when they are attached to valid units, which IMHO makes sense, because they are prefixes, not units.

Yes, that makes sense, but they still don't work in CAS mode.
I have tried them in Home and using USIMPLIFY, and it worked, in some cases.
For example, if I input USIMPLIFY(5_M*μ*s²) I will receive an "Error: bad argument type".
Yet, USIMPLIFY(5_Ms*1_μs), which is the same thing, the same unit and the same physical quantity, will work.

For some reason I couldn't figure this out until now.

[Joe Horn]

(05-16-2017 02:52 AM)rushfan Wrote:  Yes, that makes sense, but they still don't work in CAS mode.
I have tried them in Home and using USIMPLIFY, and it worked, in some cases.
For example, if I input USIMPLIFY(5_M*μ*s²) I will receive an "Error: bad argument type".
Yet, USIMPLIFY(5_Ms*1_μs), which is the same thing, the same unit and the same physical quantity, will work.

That's because the former expression (5_M*μ*s²) is not syntactically an expression of units. It is the product of three things, none of which are valid units. 5_M is not a unit. μ is not a unit. s² is not a unit. You can't USIMPLIFY something which is neither a unit nor a valid algebraic combination of units.

The latter expression (5_Ms*1_μs) DOES work because it's a syntactically valid product of two valid units. It is NOT "the same thing" as the former expression at all. 5_Ms is a unit. 1_μs is a unit. They can be validly multiplied together to form a unit, which can therefore be USIMPLIFY'd.

[Vtile]

There is the EEX key for those, have been since atleast 1970s. Now set your calculator to ENG(ineering) display mode, which looks similar than the scientific mode, but is totally different with the display logic as it follows stricktly the SI-prefix logic.

Engineering logic as the SI-prefixes increment and decrement at the step of 10^3 (E3), except the two first housekeeping prefixes at both sides of zero. Desi, hecto, deca centi (which are skipped in ENG-mode).

Don't cry you need to learn it sooner or later, m = E-3, M=E6 etc.. The prefixes aren't applied to unit itself but the magnitude indicator before the unit, which means your number is just multiplied (or divided) with proper 10^x term (so called prefix.).

Prime does excatly what you are looking for by calculating in engineering mode (of course exponent calculations are universal, but ENG-mode shows results in SI-prefix compliant form).

5E6 * 1E-6 = 5*1*10^(6+(-6)) = 5*10^(0) = 5*1 = 5

Code:


tera     T     1000000000000     10^12   E12 
giga     G     1000000000     10^9   E9
mega M     1000000     10^6   E6
kilo     k     1000     10^3   E3
(none)     (none)     10^0   E0
milli     m     0.001     10^3    E-3
micro μ     0.000001     10^−6    E-6
nano     n     0.000000001     10^−9    E-9
pico     p     0.000000000001     10^−12    E-12

Corrected above calculation example. It were 5e6 * 5e-6, corrected to 5e6 * 1e-6