(05.04 MC)

What is the exact value of [tex]\csc \frac{2 \pi}{3}[/tex]?

A. [tex]-2[/tex]

B. [tex]\frac{2 \sqrt{3}}{3}[/tex]

C. [tex]-\frac{\sqrt{3}}{3}[/tex]

D. [tex]\frac{3 \sqrt{2}}{2}[/tex]



Answer :

To determine the exact value of \(\csc \frac{2\pi}{3}\), we first recall that cosecant is the reciprocal of the sine function. Therefore, \(\csc x = \frac{1}{\sin x}\).

Let's find \(\sin \frac{2\pi}{3}\):

1. \(\frac{2\pi}{3}\) lies in the second quadrant. The reference angle for \(\frac{2\pi}{3}\) is \(\pi - \frac{2\pi}{3} = \frac{\pi}{3}\).
2. In the second quadrant, sine is positive. Recall that \(\sin \frac{\pi}{3} = \frac{\sqrt{3}}{2}\).
3. Therefore, \(\sin \frac{2\pi}{3} = \frac{\sqrt{3}}{2}\).

Now, taking the reciprocal to find \(\csc \frac{2\pi}{3}\):

[tex]\[ \csc \frac{2\pi}{3} = \frac{1}{\sin \frac{2\pi}{3}} = \frac{1}{\frac{\sqrt{3}}{2}} = \frac{2}{\sqrt{3}} \][/tex]

We can rationalize the denominator:

[tex]\[ \frac{2}{\sqrt{3}} \cdot \frac{\sqrt{3}}{\sqrt{3}} = \frac{2\sqrt{3}}{3} \][/tex]

So, the exact value of \(\csc \frac{2\pi}{3}\) is \(\frac{2\sqrt{3}}{3}\).

The correct answer is [tex]\(\frac{2 \sqrt{3}}{3}\)[/tex].