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# Complex numbers. Watch

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1. Thanks.
2. Square your answers, do you get -15 - 8i? but it's not normal to write your angle out in terms of a decimal (which you have most likely cut off the rest of the expansion). If your using Pi, leave it in terms of Pi - much easier to deal with later on.

I would expect it to be much easier to say if a + bi was a square root of -15 - 8i, then (a + bi)^2 = -15 - 8i ....
3. .........
4. Your value for theta is wrong - 28 degrees would mean the point was somewhere in the first quadrant. As well as finding arctan(y/x), you need to consider whether you should add/subtract pi radians to the argument (since arctan(-y/-x)=arctan(y/x)).
5. (Original post by Mark13)
Your value for theta is wrong - 28 degrees would mean the point was somewhere in the first quadrant. As well as finding arctan(y/x), you need to consider whether you should add/subtract pi radians to the argument (since arctan(-y/-x)=arctan(y/x)).
Bingo.....that's where I was going wrong, I needed to do 360 - theta......thanks a lot, much appreciated

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