Texas Instruments TI-83 PLUS - Manual (Page 94)

TI-83 Plus Math, Angle, and Test Operations 91
4 Rect
4 Rect (display as rectangular) displays a complex result in rectangular
form. It is valid only at the end of an expression. It is not valid if the result
is real.
complex result 8 Rect returns a + bi .
4 Polar
4 Polar (display as polar) displays a complex result in polar form. It is valid
only at the end of an expression. It is not valid if the result is real.
complex result 8 Polar returns r e^( qi ) .