4 replies to this topic

[kurashi]

Hi,

I would like to highlight an calculation error in the calculator.

The calculator gives a solution of
x = -0.8821

for the equation of,

0.857 = (3/x^2)(x*tanh-1(x)-1).

A plot of this equation on matlab shows that the solution was -1.6 or 1.6.

Is there a problem to this?

Thank you.

Regards,
Des

[flyingfisch]

I think this may be a problem with your calculator simplifying too much. I do not own an fx-991, but i would guess that there is an option to change that

[kurashi]

I think this may be a problem with your calculator simplifying too much. I do not own an fx-991, but i would guess that there is an option to change that

hmm. weird thing is, I will get the correct answer if I insert,

0.857 = (3/x^2)(x*(cosh(x)/sinh(x))-1)

strange.

Edited by kurashi, 18 April 2012 - 05:42 AM.

[MicroPro]

Hi!
The calculator is giving you the correct answer. Are you sure what you tried on Matlab was correct?
By the way: tanh-1(x) ≠ cosh(x)/sinh(x) ... (Maybe typos?)

[Xerxes]

Plotting y=(3/x^2)(x*tanh-1(x)-1)-0.857 confirms that the FX-991ES gives a correct solution.

The "tanh-1" function is only defined for arguments between -1 and 1, so 1.6 cannot be the solution.