IIT JEE , AIEEE Forum - Mathematics , Vectors

tejasvi2389

suppose a^, b^, c^ are 3 vectors of unit lengths every pair of which are inclined to each other at and angle of 53degrees. If a^Xb^= pa^+qb^+rc^, where p,q,r are scalars and q^2 as a rational number in the reduced form equals m/n then find m+n. reply soon.

kghedriu

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kghedriu

kghedriu

In this problem, I am representing the vectors a^,b^,c^ by a,b,c respectively.

Given: aXb=pa+qb+rc

so, 0=p+3/5 q+3/5 r .........(1) (apply dot product with a)

similarly, 0=3/5p +q + 3/5r..........(2) (apply dot product with b)

subtracting (1) and (2) gives: p=q

substituting this in any one of the above equations gives r = -(8/3)q

now, applying modulus on both sides for the given equation gives:

16/25 = p^2 + q^2 + r^2+ 2(p.q+q.r+r.p)

now, u know that each have 53deg angle between them,

applying p=q and r=-(8/3)q,

we get, q^2=9/55 = m/n

Hence, m+n=64

Now, dont forget to see the above mentioned message. PLEEEZE

kghedriu

Thanx for giving me ur email add

I'll contact u soon......

By the way dont hesitate to ask if the solution is not clear

And, instead of calling me kghedriu, u can call me kgh (or) harsha

................HARSHA

vish0001

hye harsha, can u solve my doubt regarding rotational mechanics as well ?? please ?!!

kghedriu

I am sorry to inform this to u vish,..... I donot know much about rotational dynamics.....But if u have any doubt regarding to units and dimensions, kinematics, particle dynamics, fluids, thermo dynamics, heat transfer, relative motion, friction, vectors, 3-d geometry,trigonometry, calculus, analytical geometry of class XI, stoichiometry,gaseous state, mole concept, chemical bonding, nomenclature, isomerism.... I will be ready to help u (cos i m of class XI, I donot know abt rotational dynamics).....Once again, I am extremely sorry cos i m helpless in this case. Forgive me....................HARSHA

amar.gupta

good work kghedriu

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