Question

Find the number of solutions of the equation $\cos 3x=0,\text{for}x\in [0,2\pi ]=$

• A. 6.0
• B. 6.00
• C. 6
• D. 06
• E. 06.0

Answer 1

Answer: (A), (B), (C), (D), (E)

Number of solutions are the numbers of points of intersection of $y=\cos 3x$ and $y=0$ in the interval $[0,2\pi ]$.
Fundamental function of $y=\cos 3x$ is $\cos x.$

Graph of $\cos x$

Transforming this graph to $\cos 3x$ by shrinking it along the x axis by 3 units. We get,
From the above graph we can say that the number of points of intersection of $y=\cos 3x$ and $y=0$ in the interval $[0,2\pi ]$ is $6.$