Question

If $\overset{\rightarrow}{A} \times \overset{\rightarrow}{B} = \overset{\rightarrow}{B} \times \overset{\rightarrow}{A}$ then the angle between A and B is

• A. π / 2
• B. π / 3
• C. π
• D. π / 4

Answer 1

Answer: (C)

π

Answer 2

We know that $\overset{\rightarrow}{A} \times \overset{\rightarrow}{B} = - (\overset{\rightarrow}{B} \times \overset{\rightarrow}{A})$ because the angle between these two is always 90°.

But if the angle between $\overset{\rightarrow}{A}$ and $\overset{\rightarrow}{B}$ is 0 or π .

Then $\overset{\rightarrow}{A} \times \overset{\rightarrow}{B} = \overset{\rightarrow}{B} \times \overset{\rightarrow}{A} = 0$