how come we know that i is 90 degrees or ~1.57 rad

I cannot understand how come we know this?

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- Mar 26th 2011, 10:51 AMprobladyhow come we know that i is 90 degrees or ~1.57 rad?
how come we know that i is 90 degrees or ~1.57 rad

I cannot understand how come we know this? - Mar 26th 2011, 11:03 AMPhugoid
In a way, I've already answered this question today.

But, in general, when we multiply something by , we rotate it through an angle in the complex plane.

Now, if we want to rotate something by , we would multiply it by .

Now, if you remember that , and that and .

Hence... . - Mar 26th 2011, 11:06 AMproblady
Amazing!!! Thanks

- Mar 26th 2011, 03:17 PMmr fantastic