JEE Main 2024 Physics question
If two vectors A⃗ and B⃗ having equal magnitude R are inclined at an angle θ, then
Answer: (B)
Solution
|A⃗ + B⃗|² = R² + R² + 2R²cosθ = 2R²(1 + cosθ) = 4R²cos²(θ/2), so |A⃗ + B⃗| = 2R cos(θ/2). (Also |A⃗ − B⃗| = 2R sin(θ/2).)