The correct answer is B: π/3. cos x + √3 sin x = 2(cos x · 1/2 + sin x · √3/2) = 2 sin(x + π/6) = 2 cos(x - π/3). Maximum is when x - π/3 = 0, i.e., x = π/3.
A.π/2
B.π/3✓ Correct
C.π/4
D.π/6
Explanation
cos x + √3 sin x = 2(cos x · 1/2 + sin x · √3/2) = 2 sin(x + π/6) = 2 cos(x - π/3). Maximum is when x - π/3 = 0, i.e., x = π/3.
💡 Practice unlimited NDA PYQs + AI-tracked progress on each topic. Sign up free →