Grade 11Vectors
If a b c are unit vectors such that a is perpendicular to plane BC and angle between BC is 60° then find |a + b + c|
If a b c are unit vectors such that a is perpendicular to plane BC and angle between BC is 60° then find |a + b + c|
2 Answers
Aastha Singh
DEAR STUDENT,
PFA
PFA
Isha
a is perpendicular to the plane of b and c.
Thus
a. b=0
a. c=0
Now, angle between b and c is 60
Thus, b. c =|b||c|cos60 =1.1.1/2
b. c=1/2
Hence
|a+b+c|^2 =|a|^2 +|b|^2 +|c|^2 +2(a.b+b.c+c.a)
=1+1+1+2(0+1/2+0)
=3+2×1/2 =4
Therefore |a+b+c|=2
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