OfficeOne 894 Graphic Calculator
Ok, so, it cost AUD $7, bought from Kmart, but it looks like you get what you pay for. Functionally, the calculator is similar to my Tandy EC-4020 (a re-badged Casio fx-4000P), with the added basic graphing capability. While my ancient Tandy still functions, the OfficeOne has since died, with the flex connecting the screen making bad contact and dropping pixels.
Bug 1
Tripped over this when calculating the bond angle in methane, the tetrahedral angle. First, in calculator-like format, with the calculators response at the end:
- Deg:2tan-1√2 = 109.4712206
- Deg:90 + sin-1(3-1) = 109.4712206
- Deg:90 + sin-1(3-1) - 2tan-1√2 = 2e-09
- Deg:sin-1(3-1) + 90 - 2tan-1√2 = 2e-09
- Deg:2tan-1√2 - 90 - sin-1(3-1) = 19.13138372 huh?
Those last three lines should be approximately zero, since [math]\displaystyle{ 2\cdot\arctan \sqrt{2} = 90 + \arcsin \tfrac{1}{3} }[/math] but no matter how many parenthesis I put in, that last line refuses to work. Interestingly, switching to radians makes it work:
- Rad:2tan-1√2 - Π÷2 - sin-1(3-1) = -2.4e-11
Bug 2
The random number generator is fine when running interactively, but when run in a tight loop, values tend toward 0 or 1.
Scl:-1000→A:Lbl 0:Ran# dt :Isz A:Goto 0
Let's have a look at some of the statistics variables:
- [math]\displaystyle{ n = 1000 }[/math]
- [math]\displaystyle{ \sum{x} = 598 }[/math]
- [math]\displaystyle{ \sum{x^2} = 357.604 }[/math]
- [math]\displaystyle{ \bar x = 0.598 }[/math]
- [math]\displaystyle{ x\sigma _{n-1} = 0 }[/math]
Ok, that's unexpected.
See Also
- Casio fx-4000P User Manual at usersmanualguide.com.
