Class 12 Vector Algebra · Conceptual Answer1 Marksdirection_cosines
Class 12 Maths · Vector Algebra · Conceptual Answer #98
A unit vector makes angles π/3 with i, π/4 with j, and an acute angle θ with k. Find θ.
✅ Step-by-Step Solution
Final Answer: π/3
- Direction cosines satisfy cos²(π/3)+cos²(π/4)+cos²θ=1, hence cos²θ=1/4. Acuteness gives cos θ=1/2.
- π/3
📋 CBSE Stepwise Marking Scheme
- [0.5 marks] Direction cosines satisfy cos²(π/3)+cos²(π/4)+cos²θ=1, hence cos²θ=1/4. Acuteness gives cos θ=1/2.
- [0.5 marks] π/3
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