Solution 28330: Converting an Imaginary Number From Decimal to Fraction on TI-84 Plus Family and TI-Nspire™ in TI-84 Plus mode.
How do I convert an imaginary number from decimal to fraction on a TI-84 Plus family or TI-Nspire in TI-84 Plus mode?The TI-84 Plus family and TI-Nspire in TI-84 Plus mode can convert imaginary numbers to fractions. However, when using the latest TI-84 Plus family OS or TI-Nspire OS, converting an imaginary value from decimal to fraction the ►FRAC command must be used.
Example: Convert .5i to a fraction.
1) Press [.]  [2ND] [i].
2) Press [MATH]  [ENTER].
Please see the TI-84 Plus family guidebook for additional information.
Please Note: Users with TI-Nspire in TI-84 Plus mode may use the TI-84 Plus guidebook.