There are three supported notations for complex numbers in rectangular
form. The default is as a pair of real numbers enclosed in parentheses
and separated by a comma: ‘`(a,b)`’. The `d c`
(`calc-complex-notation`

) command selects this style.

The other notations are `d i` (`calc-i-notation`

), in which
numbers are displayed in ‘`a+bi`’ form, and `d j`
(`calc-j-notation`

) which displays the form ‘`a+bj`’ preferred
in some disciplines.

Complex numbers are normally entered in ‘`(a,b)`’ format.
If you enter ‘`2+3i`’ as an algebraic formula, it will be stored as
the formula ‘`2 + 3 * i`’. However, if you use `=` to evaluate
this formula and you have not changed the variable ‘`i`’, the ‘`i`’
will be interpreted as ‘`(0,1)`’ and the formula will be simplified
to ‘`(2,3)`’. Other commands (like `calc-sin`

) will *not*
interpret the formula ‘`2 + 3 * i`’ as a complex number.
See Variables, under “special constants.”