HP-35s complex numbers in polar mode

[ijabbott]

[sqrt] is an operation key, not a number entry key.

You could enter the number as two numbers and multiply them together:

2
[sqrt]
1Θ45
[x]

Or enter the approximate value of sqrt(2) as part of the number:

1.41421356237Θ45
[enter]

Or just enter it in rectangular form since you already know it:

1i1
[enter]