Jump to content

Complex Geometry

Featured Replies

Ok so I have 2 points

 

A = 2 + 3j

C = 4 + 7j

 

on our argand diagram they make an equailateral triangle with a point (or more precisely either of 2 points) which I'll call z

 

Now I know;

[math]

 

ABC = arg ( \lambda ) = arg (\frac{a - b}{c-b})

 

 

 

[/math]

so

[math]

arg(\lambda) = \frac{\pi}{3}

 

[/math]

 

and

 

[math]

\lambda = \frac{a-b}{c-b}

[/math]

[math]

\lambda = \frac{(z-(4+7j))-((4+7j)-(2+3j))}{(z-(2+3j))-((4+7j)-(2+3j))}

[/math]

[math]

\lambda = \frac{z-6-11j}{z-4-j}

[/math]

 

 

No where do I go from here; solve simultaneously, or am I using the completely wrong method?

 

I've attatched a sketch of the argand diagram.

argand.jpg

Ok so I have 2 points

 

A = 2 + 3j

C = 4 + 7j

 

on our argand diagram they make an equailateral triangle with a point (or more precisely either of 2 points) which I'll call z

 

Now I know;

[math]

 

ABC = arg ( \lambda ) = arg (\frac{a - b}{c-b})[/math]

I'm not familiar with this. "ABC" is a real number. What number? The cosine of the angle between sides?

 

I would be more inclined to use modulus than arg: |A- C|= |-2- 4j|= [math]\sqrt{4+ 16}= \sqrt{20}[/math]. Since this is an equilateral triangle, we must have also |z- A|= |z- C|=[math]\sqrt{20}[/math] also. Letting z= x+ yj, [math]\sqrt{(x-2)^2+ (y-3)^2}= \sqrt{20}[/math] and [math]\sqrt{(x-4)^2+ (y-7)^2}= \sqrt{20}[/math].

 

Of course, those immediately give [math](x- 2)^2+ (y-3)^2= 20[/math] and [math](x- 4)^2+ (y- 7)^2= 20[/math]. You should be able to see that, after you multiply those out, the [math]x^2[/math] and [math]y^2[/math] terms cancel and you have two linear equations to solve for x and y.

 

 

so

[math]

arg(\lambda) = \frac{\pi}{3}

 

[/math]

 

and

 

[math]

\lambda = \frac{a-b}{c-b}

[/math]

[math]

\lambda = \frac{(z-(4+7j))-((4+7j)-(2+3j))}{(z-(2+3j))-((4+7j)-(2+3j))}

[/math]

[math]

\lambda = \frac{z-6-11j}{z-4-j}

[/math]

 

 

No where do I go from here; solve simultaneously, or am I using the completely wrong method?

 

I've attatched a sketch of the argand diagram.

By asking for z and x.

1) substract the 2nd addend on the left-hand side from both sides

2) divide both sides by 2

Archived

This topic is now archived and is closed to further replies.

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.

Configure browser push notifications

Chrome (Android)
  1. Tap the lock icon next to the address bar.
  2. Tap Permissions → Notifications.
  3. Adjust your preference.
Chrome (Desktop)
  1. Click the padlock icon in the address bar.
  2. Select Site settings.
  3. Find Notifications and adjust your preference.