• Support PF! Buy your school textbooks, materials and every day products Here!

Help with squaring geometry help

  • Thread starter PiRsq
  • Start date
  • #1
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?
 

Answers and Replies

  • #2
Hurkyl
Staff Emeritus
Science Advisor
Gold Member
14,916
19
Try squaring everything.
 
  • #3
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
 
  • #4
Hurkyl
Staff Emeritus
Science Advisor
Gold Member
14,916
19
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?
 
  • #5
110
0
Thanks man
 

Related Threads on Help with squaring geometry help

  • Last Post
Replies
1
Views
700
  • Last Post
Replies
7
Views
845
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
11
Views
4K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
4
Views
1K
Replies
5
Views
10K
  • Last Post
Replies
1
Views
5K
Replies
4
Views
4K
Top