My TI84 plus silver edition calculator is giving me an incorrect sign whenever I do an exponential function. When I type in -25^2, it gives me -625 instead of 625. How do I fix this?

This was asked two years ago, but if anyone finds this page maybe this will help:
Instead of 1E99, try using 10^99. They have the same value but it would appear that some calculators have trouble with 1E99. It fixed it for me.

Try to find a classmate who has the same calculator (TI84 Plus or TI84 Plus Silver Edition) and effect a transfer of the OS from the classmate's calculator using an IO cable.
Alternatively, download the new version of TI Connect (version 4.) and install it on your computer. Then connect your calculator to the computer through the USB cable. When it recognizes the calculator click the update button in TI Connect interface and select update OS. Good luck.

When calculating trigonometric functions you should pay attention to the angle unit used. The TI84 PLUS/SE can use two units: the radian and the degree, As to rounding I do not see why it would ruin your answers which are approximate anyway. Just choose float whithout specifying the number of decimal digits, then when a result is displayed round it yourself to the desired accuracy.

To set the angle unit press MODE, then use down arrow to move highlight to the line RADIAN DEGREE and select the one you want.

If you want to raise a number to another, use the ^ key located just above the divide key.
For natural antilogarithm (exponentiation of e), use 2ND [e^x] (the shifted function of the LN key).
For common antilogarithm (exponentiation of 10), use 2ND [10^x] (the shifted function of the LOG key).
To enter a decimal exponent as part of a number, use 2ND [EE] (the shifted function of the comma key, located just above the 7 key.

Press Apps. scroll Down to reach Inequalz. Select it and press ENTER.In subsequaent screen select the option that uninstalls Inequalz.

Make sure you have the proper angular mode set. The TI-84 can work with degrees or radians.

Press MODE to bring up the mode screen. Use the arrow keys to highlight either "Radian" or "Degree" on the third line and press ENTER. Press 2ND [QUIT] to exit the mode screen.

If this doesn't do it, please reply to this post giving an example of a calculation and the answer you're getting from the calculator.

Press APPS go to Inequalz select Quit Inequal

Sorry, but that feature is not implemented on the TI84 family of calculators. No key or command will instruct the calculator to perform such a calculation.
You may deplore such a shortcoming, but please, do not hold me responsible for it.

there is a fuse after the USB connector on the mainboard it could be that it burned.
i fix this calculators

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Maybe the batteries are dead?