What is the exact value of [tex]\tan \frac{7 \pi}{12}[/tex]?

A. [tex]-(2-\sqrt{3})[/tex]
B. [tex]-(2+\sqrt{3})[/tex]
C. [tex]2-\sqrt{3}[/tex]
D. [tex]2+\sqrt{3}[/tex]



Answer :

To find the exact value of [tex]\(\tan \frac{7\pi}{12}\)[/tex], we can use the angle sum identity for tangent. Let's begin by breaking down [tex]\(\frac{7\pi}{12}\)[/tex] into the sum of two angles whose tangent values we know.

Notice that:
[tex]\[ \frac{7\pi}{12} = \frac{3\pi}{4} + \frac{\pi}{3} \][/tex]

We can now use the tangent sum formula:
[tex]\[ \tan(A + B) = \frac{\tan A + \tan B}{1 - \tan A \tan B} \][/tex]

Here, let [tex]\( A = \frac{3\pi}{4} \)[/tex] and [tex]\( B = \frac{\pi}{3} \)[/tex].

First, we need to know the values of [tex]\(\tan A\)[/tex] and [tex]\(\tan B\)[/tex]:
[tex]\[ \tan \frac{3\pi}{4} = -1 \][/tex]
[tex]\[ \tan \frac{\pi}{3} = \sqrt{3} \][/tex]

Now, apply these values in the tangent sum formula:
[tex]\[ \tan \left( \frac{3\pi}{4} + \frac{\pi}{3} \right) = \frac{\tan \frac{3\pi}{4} + \tan \frac{\pi}{3}}{1 - \tan \frac{3\pi}{4} \tan \frac{\pi}{3}} \][/tex]
[tex]\[ \tan \left( \frac{3\pi}{4} + \frac{\pi}{3} \right) = \frac{-1 + \sqrt{3}}{1 - (-1) (\sqrt{3})} \][/tex]
[tex]\[ \tan \left( \frac{3\pi}{4} + \frac{\pi}{3} \right) = \frac{-1 + \sqrt{3}}{1 + \sqrt{3}} \][/tex]

To simplify this expression, multiply the numerator and the denominator by the conjugate of the denominator:
[tex]\[ \tan \left( \frac{3\pi}{4} + \frac{\pi}{3} \right) = \frac{(-1 + \sqrt{3})(1 - \sqrt{3})}{(1 + \sqrt{3})(1 - \sqrt{3})} \][/tex]
[tex]\[ \tan \left( \frac{3\pi}{4} + \frac{\pi}{3} \right) = \frac{(-1 + \sqrt{3})(1 - \sqrt{3})}{1 - 3} \][/tex]
[tex]\[ \tan \left( \frac{3\pi}{4} + \frac{\pi}{3} \right) = \frac{(-1 + \sqrt{3})(1 - \sqrt{3})}{-2} \][/tex]

Now, simplify the numerator:
[tex]\[ (-1 + \sqrt{3})(1 - \sqrt{3}) = -1 + \sqrt{3} - \sqrt{3} + 3 = -1 + 3 = 2 \][/tex]

So, we have:
[tex]\[ \tan \left( \frac{3\pi}{4} + \frac{\pi}{3} \right) = \frac{2}{-2} = -1 \][/tex]

We further simplified the function incorrectly, so let's correct that in proper terms:

For exact values:
[tex]\[ \tan \left( \frac{3\pi}{4} + \frac{\pi}{3} \right) = \frac{2}{-2} = -\frac{1}{\sqrt{3}} \][/tex]

It appears bizarre without conjugate setup, when instead calculated:
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