Suppose [tex]\tan(x) = \frac{7}{2}[/tex] where [tex]180^{\circ} \leq x \leq 270^{\circ}[/tex]. What is the value of [tex]\sin(2x)[/tex]?

A. [tex]\frac{7}{\sqrt{53}}[/tex]
B. [tex]\frac{14}{\sqrt{53}}[/tex]
C. [tex]\frac{28}{53}[/tex]
D. [tex]\frac{49}{53}[/tex]



Answer :

Given that [tex]\(\tan(x) = \frac{7}{2}\)[/tex] and [tex]\(180^\circ \leq x \leq 270^\circ\)[/tex], which means [tex]\(x\)[/tex] is in the third quadrant where both sine and cosine are negative.

We start by using the identity of tangent:
[tex]\[ \tan(x) = \frac{\sin(x)}{\cos(x)} = \frac{7}{2} \][/tex]

In the third quadrant, both [tex]\(\sin(x)\)[/tex] and [tex]\(\cos(x)\)[/tex] are negative. We can represent [tex]\(\sin(x)\)[/tex] as [tex]\(-7k\)[/tex] and [tex]\(\cos(x)\)[/tex] as [tex]\(-2k\)[/tex] for some positive constant [tex]\(k\)[/tex].

By using the Pythagorean identity:
[tex]\[ \sin^2(x) + \cos^2(x) = 1 \][/tex]

Substituting [tex]\(\sin(x) = -7k\)[/tex] and [tex]\(\cos(x) = -2k\)[/tex] into the identity:
[tex]\[ (-7k)^2 + (-2k)^2 = 1 \][/tex]
[tex]\[ 49k^2 + 4k^2 = 1 \][/tex]
[tex]\[ 53k^2 = 1 \][/tex]

Solving for [tex]\(k\)[/tex]:
[tex]\[ k^2 = \frac{1}{53} \][/tex]
[tex]\[ k = \frac{1}{\sqrt{53}} \][/tex]

Now, substituting [tex]\(k\)[/tex] back into [tex]\(\sin(x)\)[/tex] and [tex]\(\cos(x)\)[/tex]:
[tex]\[ \sin(x) = -7k = -\frac{7}{\sqrt{53}} \][/tex]
[tex]\[ \cos(x) = -2k = -\frac{2}{\sqrt{53}} \][/tex]

The double angle formula for sine is:
[tex]\[ \sin(2x) = 2 \sin(x) \cos(x) \][/tex]

Substituting [tex]\(\sin(x)\)[/tex] and [tex]\(\cos(x)\)[/tex] into this formula:
[tex]\[ \sin(2x) = 2 \left(-\frac{7}{\sqrt{53}}\right) \left(-\frac{2}{\sqrt{53}}\right) \][/tex]
[tex]\[ \sin(2x) = 2 \cdot \frac{14}{53} \][/tex]
[tex]\[ \sin(2x) = \frac{28}{53} \][/tex]

So, the value of [tex]\(\sin(2x)\)[/tex] is:
[tex]\[ \boxed{\frac{28}{53}} \][/tex]