Question

The vectors (A + B) and (A - B) are at right angles to each other. This is possible under the condition.

Options

• |A| = |B|

• A · B = 0

• A · B = 1

• A × B = 0

Answer 1

|A| = |B|

Explanation:

Vectors (A + B) and (A - B) are at right angle to each other, therefore

(A + B) · (A - B) = 0

A · A + B · A - A · B - B · B = 0

|A| + BA cos θ - AB cos θ - |B|² = 0

|A|² = |B|² 

Hence, |A| = |B|