IIT JEE , AIEEE Forum - Mathematics , Vectors

Tejal

1) If magnitude of u^-=3 is equally inclined to the unit vectorsi^- ,j^- ,& k^-; find u^- .

raman_1290

Let u = x i^ + y j^ + z k^

and x² + y² + z² = 9 .....................(1)

(u).(i^) = x

3.1.cos

= x ; x = 3cos

sinilarly, y = 3cos

and z = 3cos

using values of x, y and z in (1)

3cos²

= 1

Cos

= 1/

3

therefore x = y = z = 3/

3 =

3

hence, u =

3i^ +

3j^ +

3k^.

iitkgp_bipin

u = xi + yj + zk

Then |u| =

(x²+y²+z²) = 3 (given)

since they are equally inclined to axes

x=y=z

Hence

(3x²) = 3

which gives x =

3

Hence u =

3i +

3j +

3k

Best Wishes

vivacious7

hey ppl

plz help me out for vectors i just hate it

so plz tell wats imp n how do study it

plz

kghedriu

Hey, dont feel bad 4 this....if u love the chapter, things will automatically come to ur side....do what i said, u'll find the difference.

kghedriu

as far as ur problem is concerned, vivacious,,

u must understand that the basic chapters of vectors, addition and subtraction r eezy.

in the case of other chapters, all u need to do is get the formulae byheart..bcos this is not a conceptual or logical chapter...

Then, go for a lot of sums, preferably in the book of arihant and shanti narayan..

this is reqd bcos only then u can understand which one is to be applied when...

for objective qns, it would be better to do M.L.Khanna first to develop some ideas....

kghedriu

Any more help, do ask me.. and if my sugesstions look like benefitting u,

do give me ur votes dude!

vivacious7

well how to start it

i dont get anything wen i sit wid tis

magiclko

hey gautham , she's a gal...

so miss vivacious

, u hate vectors, hmmm.... study it yaar... its too easy, jst go thru the chapter once frm any standard buk, nd u'll get to knw it on ur own... thr's nothin such in chapter which u wont understand.... mainly go thru scalar nad vector triple product.... most of the questions are based on them, nd then learn (with understanding), the equations for line and plane, thats all in the chapter!!!

knock back to me, if u need any help in the sums for the chapter!!!!!!!!!!

kghedriu

sorry 4 th

at

vivacious7

hey

manasi baby

dont do masti here

yaha only prob solvin

magiclko

no masti dear, question to pucho yaar... then only i'll reply naa!!!! how can i reply any of ur question, if u dnt ask me!!!!

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