The angle between two lines whose direction ratios are and is equal to:

Answer and explanation

Correct answer: A.

  1. Step 1: The cosine of the angle between two vectors and is .
  2. Step 2: Compute scalar product: .
  3. Step 3: Since the dot product is identically zero, . The two lines are orthogonal.
Answer
.
Why not the others: uses ; neglects the negative sign; corresponds to .

Practise more Three dimensional geometry.

Free questions with an explanation for every one, and full timed JEE Main mock tests.