Q.

The directions cosines of two lines are connected by relations l+m+n=0 and 4l is the harmonic mean between m and n then

see full answer

Want to Fund your own JEE / NEET / Foundation preparation ??

Take the SCORE scholarship exam from home and compete for scholarships worth ₹1 crore!*
An Intiative by Sri Chaitanya

a

l1l2+m1m2+n1n2=32

b

l1l2+m1m2+n1n2=-32

c

l1l2+m1m2+n1n2=12

d

l1l2+m1m2+n1n2=-12

answer is B.

(Unlock A.I Detailed Solution for FREE)

Ready to Test Your Skills?

Check your Performance Today with our Free Mock Test used by Toppers!

Take Free Test

Detailed Solution

l+m+n=04l=2mnm+n⇒2lm−mn+2ln=0by eliminating n, we get2lm2−lm−1=0⇒l1m1=1,l2m2=−12 and ⇒n1n2=−2∴l1l2+m1m2+n1n2=1−12−2=−32
Watch 3-min video & get full concept clarity
score_test_img

Get Expert Academic Guidance – Connect with a Counselor Today!

whats app icon