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# OCR - FP1 (Loci) watch

1. So I am doing FP1 and I understand all of it besides Loci. Question 2 from the paper can be used as an example. I know that the |a| is 5 because [(3^2+4^2)^1/2] but i don't understand arg(a) and any of 2(ii).
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3. (Original post by mhamzan786)
So I am doing FP1 and I understand all of it besides Loci. Question 2 from the paper can be used as an example. I know that the |a| is 5 because [(3^2+4^2)^1/2] but i don't understand arg(a) and any of 2(ii).
The argument of a complex number is the angle in radians from the positive real axis to the point on the Argand diagram. It's anti-clockwise positive.

Now here is in the first quadrant so to three decimal places.

is a circle with centre and radius which you said you found. It means "all the complex numbers on the Argand diagram that are exactly away from ."

is a half-line. It means roughly "all the complex numbers on the Argand diagram that, when you minus 3 from them, have the same argument as does."

I've written about it in more detail on my website here: https://www.furthermathstutor.co.uk/...x-numbers.html

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