where the imaginary part, j = √(-1) or j² = -1; j³ = j²∙j = - j.
Now each rotation of 90° is a multiplication by ' j '.
Thus a rotation of 180° ~ j² ; 270° ~ j³.
Using these you can do the rest (by multiplying with your number, that is now called a Complex number with a real & another imaginary part in it; ex.: j(-2+j5) ).
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Verified answer
Write the number as
(-2,5) = -2+j5
where the imaginary part, j = √(-1) or j² = -1; j³ = j²∙j = - j.
Now each rotation of 90° is a multiplication by ' j '.
Thus a rotation of 180° ~ j² ; 270° ~ j³.
Using these you can do the rest (by multiplying with your number, that is now called a Complex number with a real & another imaginary part in it; ex.: j(-2+j5) ).