My calculator Casio fx-991ES don't respond to any buttons it don't show any thing on the screen after I was solving an integral can you help me plz

SOURCE: mode change

Hello,
Just so that we know what we are talking about. The natural display is the display mode in which fractions appear on two lines, radicals appear as radicals, log can be calculated in any base, etc. If that is what you understand by Natural Display, we are in agreement.
To set this mode, you turn calculator ON and press [SHIFT][MODE] (setup). The option is called MathIO, and it has the number 1.
Thus [SHIFT][MODE][1:MathIO].
Hope it helps.

SOURCE: when i press the MODE button in my CASIO fx - 911ES

Hello,
Just in case : Press [SHIFT][CLR] (9) [3: ALL] to reset the calculator and try [MODE] again.
If that does not work, your calculator may be defective or a fake (not the genuine article). If at all possible, return it to where you bought it and get a refund.

Here is a picture of the FX-115ES, its face looks like the 991ES. Hope I am mistaken.

SOURCE: can you show how to convert pola to rectangular o

Hello,
To avoid errors make sure that the angle unit is THE ONE required by your problem. To verify or to change the angle unit press [SIFT][MODE] and select [3: Deg] for degrees, [4:Rad] for radians, or [5:Grad] for grads.

Convert from rectangular to polar

[SHIFT][+] (Pol) . Screen displays Pol(
You enter the X-coordinate, and the Y coordinate separated by a comma, then you close the parenthesis and press [=].

Exemple: Polar coordinate of the point (1,1)
Pol( 1, 1) gives
r=1.414213562 (square root of 2)
θ=45

Here is how you enter it
Press [SHIFT][MODE][2:LineIO]
[SHIFT][POL] 1 [SHIF] [,] 1 [)] [=]

The screen displays
Pol(1,1)
r= 1.414213562
θ= 45

Convert from polar to rectangular coordinates

Rec ( radius, angle) =

Exemple: Recatngular coordinates of (r=3, θ=60°)
[SHIFT][Rec] 3 [SHIFT][,] 60 [ ) ] [=]
The screen displays
Rec(3,60)
X= 1.5
Y= 2.598076211

Hope it helps.

Testimonial: "thanx that was very helpful"

SOURCE: how can we do linear interpolation in casio fx-991ES calculator

how solve interpolation by casio fx 991 ex

SOURCE: i can't find the EXP button on my Casio fx-83GT

Your question is slightly ambiguous.

If you refer to the exponential function (power to base e = 2,7182818...), the key sequence is [SHIFT] [ln]. (rightmost button column, two rows below the ON key).

If you refer to a key allowing to enter powers of 10, like in 3,14 x 10²³, see the button labeled

its located in the bottom button row, center column.