NCERT Class 12 · Ch 10 Miscellaneous Exercise · Q17
NCERT Class 12 Maths · Chapter 10 Vector Algebra · Miscellaneous Exercise Question 17
Unit vectors a,b make angle θ. When is a+b also a unit vector?
💡 Concept Hints
- Write the vector components and identify the required direction or geometric relation.
- Use the magnitude, dot-product, cross-product or section formula that matches the requested quantity.
✅ Step-by-Step Solution
Final Answer: D: θ=2π/3.
- |a+b|²=1+1+2cos θ.
- Set this equal to 1 to get cos θ=−1/2; in [0,π], θ=2π/3.
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