# Complex number when using variables

1 view (last 30 days)
user86753 on 11 Apr 2020
Commented: user86753 on 11 Apr 2020
I am getting two different answers in MATAB 2017a. If I compute it directly in the Command Window vs assigning the variables x,y, I get a complex answer?
-50.8478 ^ -1.017
ans =
-0.0183959070209519
K>> x = -50.8478; y = -1.017
K>> x^y
ans =
-0.0183696777893977 + 0.000982004601423454i
user86753 on 11 Apr 2020
Thanks!

Steven Lord on 11 Apr 2020
That's correct. The unary minus operator (before 50.8478) is at precedence level 4. The matrix power operator with unary minus (between 50.8478 and 1.017) is at precedence level 3. So:
-50.8478 ^ -1.017
is equivalent to:
-(50.8478^-1.017)
The expression inside the parentheses is real.
When you use variables:
x = -50.8478;
y = -1.017
x^y
that is equivalent to:
(-50.8478)^(-1.017)
which gives a complex result.

James Tursa on 11 Apr 2020
Edited: James Tursa on 11 Apr 2020
Operator precedence
>> -50.8478 ^ -1.017
ans =
-0.0184
>> (-50.8478) ^ -1.017
ans =
-0.0184 + 0.0010i
The ^ operator has higher precedence than the - operator when typed in at the command line.

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