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If a,b and c are three vectors of equal magnitude. The angle between each pair of vectors is π3 such that ∣a+b+c∣=√6. Then |a| is equal to

A. 2
B. −1
C. 1
D. √6

1 Answer

7 votes

The magnitude of vector a (|a|) is determined as 1 (Option C).

How to calculate the magnitude of vector a?

The magnitude of vector a is calculated by applying the formula for dot product of two vectors.

a · b = |a| · |b| · cos(θ)

The given expression.

|a + b + c| =√6

|a + b + c|² = (√6)²

(a + b + c) · (a + b + c) = 6

The expression is simplified as follows;

|a|² + |b|² + |c|² + 2(a·b + b·c + c·a) = 6

a.b = |a| · |b| cosθ

θ = π/3

θ = 180/3

θ = 60

Also, |a| = |b| = |c| = y

|a|² + |b|² + |c|² + 2(a·b + b·c + c·a) = 6

|a|² + |b|² + |c|² + 2(|a|·|b| cosθ + |b|·|c| cosθ + |c|·|a| cosθ ) = 6

y² + y² + y² + 2(y² (1/2) + y²(1/2) + y²(1/2)) = 6

y² + y² + y² + (y² + y² + y²) = 6

6y² = 6

y² = 6/6

y² = 1

y = ±√1

y = ±1

|a| = 1

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