Let the direction cosines of two lines satisfy the equations: and .
Then the cosine of the acute angle between these lines is:
Then the cosine of the acute angle between these lines is:
- (A)
- (B)
- (C)
- (D)✓ Correct
Answer: (D)
Solution
From , we get .
Substituting into :
Factoring: .
Case 1: , so . Direction ratios: or .
Case 2: , so . Direction ratios: or .
Cosine of angle: .
Substituting into :
Factoring: .
Case 1: , so . Direction ratios: or .
Case 2: , so . Direction ratios: or .
Cosine of angle: .
JEE Main · 2026 · 23 Jan 2026 · Shift 1 · Single correct option