1) Sketch on the Argand diagram the regions which satisfy .

so now what do i do?

2) Indicate clearly on an Argand diagram the region of points that satisfy both the conditions ,

Thanks as always.!

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- January 25th 2010, 12:10 PMBabyMiloMore Complex Number
1) Sketch on the Argand diagram the regions which satisfy .

so now what do i do?

2) Indicate clearly on an Argand diagram the region of points that satisfy both the conditions ,

Thanks as always.! - January 25th 2010, 01:39 PMmr fantastic
1) and are concentric circles. is the area in between them.

2) is a circle. is the line x = 5. and is the area between the circle and the line (you will need to decide which of the two possible areas it is ....)

By the way, all these relations have a very simple geometric interpretation which makes it easy to get the cartesian equations .... - January 25th 2010, 10:46 PMBabyMilo
- January 26th 2010, 04:18 AMHallsofIvy
Do you understand that |z| is the distance from the complex number z to the number 0= 0+ 0i? From that it follows that |a- b| is the distance between the two complex numbers a and b.

Saying that |z+ 3i|= |z- (-3i)|= 1 means that the distance from z to -3i is 1: z can be any number on the circle with center at -3i and radius 1. Saying that means that z is on or outside that circle.

Similarly |z+ 3i|= |z- (-3i)|= 4 means that the distance from z to -3i is 4: z can be any number on the circle with center at -3i and radius 4. says that z is on or inside that circle.

Similarly, means that z is a point on or inside the circle with center at 3- 4i and radius 4.

means that the distance from z to the origin is equal to the distance from z to 10. And it is an easy geometry theorem that the set of all point equidistant from two points is the perpendicular bisector of the segement between the two points. Here, that is the line perpendicular to the x-axis (real axis) at (5, 0) which is given by z= 5+ yi for any y.

is that line plus the set of points on the right side of that line so that z is closer to 10 than to 0. - January 26th 2010, 10:12 AMBabyMilo
Would this be correct for Q2 ?

thanks! - January 27th 2010, 03:40 AMmr fantastic
- January 27th 2010, 03:43 AMHallsofIvy
Your circle is correct but I don't know how you got that line- and you don't say what line it is. The set of z such that is, as I said, the

**perpendicular**bisector of the line from 0 to 10. The line containing 0 and 10, the real axis, is horizontal, so the perpendicular bisector is the**vertical**line z= 5+ yi for all y. - January 27th 2010, 06:36 AMBabyMilo
- January 27th 2010, 04:58 PMmr fantastic
- January 27th 2010, 10:48 PMBabyMilo
- January 28th 2010, 02:17 AMmr fantastic