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Complex number when using variables

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user86753
user86753 2020-4-11
评论： user86753 2020-4-11
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

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采纳的回答

Steven Lord
Steven Lord 2020-4-11
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.

更多回答（1 个）

James Tursa
James Tursa 2020-4-11
编辑：James Tursa 2020-4-11
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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