Question

The number of roots of the equation cos 3θ=0 for 0≤θ\le2π is

• A. 4
• B. 5
• C. 6
• D. 8

Hint:

Solve for the multiplied angle first, then count solutions in the interval.

Answer 1

The Correct Option is C

cos 3θ=0 ⟹ 3θ=(π)/(2)+kπ θ=(π)/(6)+(kπ)/(3) For 0≤θ\le2π, there are 6 such values.