IIT JEE , AIEEE Forum - Mathematics , Vectors

karthik_abiram

Q] Let "a" be a vector of magnitude 5.Suppose a.(b +c)=0 and a.(b-c)=0 then a vector of magnitude 45 perpendicular to both "b" vector and "c" vector is

1]{+ or -} 5 "a" vector

2]{+ or - } 9 "a" vector

3] {+ or -} 9 "(b+c)" vector

4]{+ or - } 6 "(b-c)" vector

plz give detailed steps........thank u.......

kghedriu

hey....firstly....see this soln.....if u want ne other one, i will post it the next time i log in...

firstly, the reqd vector has a magnitude 45....

and, u donno mag od b and c...so, u donno mag of b+c and b-c..

this tells tht the ans is related to a...

now, mag of a is 5....nd tht of reqd vec is 45...

so, it shud be 9a only..

hope m clear..

thank u..

Goutham.

karthik_abiram

Hey goutham,

u make it very simple and i m looking like a LKG student!{just joking}

any way if u get any other method plz post.............thank you.........

aysh

Hi Karthik,

Jus goin for a simpler method...

Take b = c and let b be perpendicular 2 a.
This makes both the equations being satisfied by vectors a, b, c.
Clearly,
a vector of magnitude 45 perpendicular to both b vector and c vector is 9a.

HOPE U LIKE IT....
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