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 Question from Cheyenne, a student: There's a question on my Summer Assignment I cant figure out. Here it is: Find the absolute Value of the complex number. -5i Please help?

Hi Cheyenne,

The modulus of a complex number $z = a + bi$ is often written $|z|$ and is defined by

$|z| = |a + bi| = \sqrt{a^2 + b^2}.$

If you plot the point $z = a + bi$ in the complex plane, sometimes called an Argand diagram, then the modulus of $z$ is the distance from the origin to $z.$ It is nicely explained with diagrams on the mathcentre site in the UK.

Penny

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