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Casio FX-991ES vs. HP 48G

posted Sep 26, 2012, 1:29 PM by Darko Križić   [ updated Sep 27, 2012, 12:12 AM ]
Recently my daughter did her homework and came to me to help her. One part of the task was to calculate the area of 

    x^4 + x^3 - 2*x^2 

in the interval of 0 and 1. The indefinive integration is

    x^5/5 + x^4/4 - 2*x^3/3

(see here). Wolfram Alpha claims that the numerical result is

    -13/60

which approximates to -2.16667. Her Casio FX-991ES calculator gives a totally different result of -1.xxx like that. Now I was unsure whom to blame. I cannot imagine that my Wolfram Alpha (Mathematica) calculates wrong. Then I opened my drawer and took out my good old HP 48G which I used a long time ago when I studied. Let's screenshots talk:

Entering the formula

And now the result

The symbolic and numerical

Ok, now I am sure, that the Casio is not working correctly. Obviously others also have problems with it. The HP was an amazing device 20 years ago, but I am "not amused", that a current calculator is not able to compete with it. Maybe my daughter should learn using the HP 48G (remember: UPN!)
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