Help with squaring geometry help

  • Thread starter PiRsq
  • Start date
110
0
x and y are vectors

If |x|=11 and |y|=23 and |x-y|=30, find |x+y|?

I tried but I couldn't get it, any hints out there guys?
 

Hurkyl

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Try squaring everything.
 
110
0
I did

|x|^2 + |y|^2 = |x+y|^2

Then |x+y|=25.6 units

But my book's answer says 16 units...I dont get it
 

Hurkyl

Staff Emeritus
Science Advisor
Gold Member
14,829
14
That formula only works when x and y are perpendicular vectors.

Recall that for any vector z:

|z|^2 = z * z

So what should |x + y|^2 and |x - y|^2 be?
 
110
0
Thanks man
 

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