Home » Ask & Discuss » Mathematics. » Vectors « Back to Discussion

Vectors

New kid on the Block

Joined:	24 Mar 2008
Post:	19

9 Apr 2008 12:20:57 IST

0 People liked this

484

Unit vectors

None

If a^ , b^ , c^ are unit vectors , then the max value of | a^ + b^ - c^ |² + | b^ + c^ - a^|²+ | c^ + a^ - b^|² must be:

(a) 9 (b) 12 (c) 15 (d) none of these

pls reply.

Share this article on:

Comments (6)

Sujay

New kid on the Block

Joined: 24 Mar 2008

Posts: 19

9 Apr 2008 12:35:03 IST

Like 0 people liked this

someone pls tell...

Anup

Hot goIITian

Joined: 9 Nov 2006

Posts: 127

9 Apr 2008 12:36:51 IST

Like 3 people liked this

is the ans c..12
if yes method .........
since the expression is symmetric in a,b,c
it can attain max value when a,b,c are equally inclined to each other i.e angle between them is 120 degrees...............

simplifying the expression...........
3(1+1+1-2*1/2 +4*1/2)=12

ashish gupta

Scorching goIITian

Joined: 6 Apr 2008

Posts: 221

9 Apr 2008 12:37:30 IST

Like 0 people liked this

its 12 ..
it was asked in fiitjee full test xi last sunday (paper 1,ques 1)

want solution .. rate me then

kaushik krishna

Blazing goIITian

Joined: 19 Apr 2007

Posts: 392

9 Apr 2008 12:40:20 IST

Like 0 people liked this

ans is 12...anups explanation is right

zamuka chen

Scorching goIITian

Joined: 10 Mar 2007

Posts: 216

9 Apr 2008 12:40:36 IST

Like 0 people liked this

bilkul sahi anup, mein bhi yahi type kar raha tha.....

Sujay

New kid on the Block

Joined: 24 Mar 2008

Posts: 19

9 Apr 2008 12:43:54 IST

Like 0 people liked this

thnx..

Quick Reply

Reply

	Some HTML allowed.
	Keep your comments above the belt or risk having them deleted.
	Signup for a avatar to have your pictures show up by your comment
	If Members see a thread that violates the Posting Rules, bring it to the attention of the Moderator Team