# A LEVEL MATHEMATICS

### The Mailbox

#### Discovering vertices of a rectangle in an Argand diagram

 Posted by White Group Mathematics on August 4, 2015 at 9:40 PM

Hi Mr Koh,

How do I do this question- In an Argand diagram, the points A, B, C and D represent the complex numbers a,  -2+5i,  c   and  3/2 - 1/2 i   respectively. Given that ABCD is a rectangle described in the clockwise sense with BC=2AB, find a and c.

I tried drawing B and D on the same diagram but they don't even have a right angle between them, so how can it form a rectangle? And I can't place points A and C on the diagram because they said ABCD is read clockwise but it is also mentioned BC=2AB....so I am lost. Haha. Thanks Mr Koh!

Student X

Based on the construct described, the rectangle's length is twice its breadth. I would recommend drawing a generic upright rectangle instead of trying to place the points specifically in Argand space. Do note that vectors are involved in the solving process. I have drafted a solution template for you:

Hope this helps. Peace.

Best Regards,

Mr Koh

Categories: Math Queries

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