Question

Let a, b and care unit vectors suppose that a. b=a.c=0 and the angle between band c is 39° then prove that a=2 ( b cross c)

Answer 1

Answer:

Explanation:

Since A.B=A.C=0

∴A is ⊥ to the plane B and C

Also, B×C=∣B∣∣C∣sin  

6π

n = 2 1 ​n

But A=  n ,both being unit vectors ⊥ to the plane of B and C

A=±2(B×C)