c) First, we need to convert 7π/6 radians to degrees. π radians are equivalent to 180°, then:
![(7\pi)/(6)radians=(7\pi)/(6)radians\cdot\frac{180\text{ \degree}}{\pi\text{ radians}}=210\text{ \degree}](https://img.qammunity.org/2023/formulas/mathematics/college/hiwwm9gg0zryi9zidnmslz09u0mh2odljh.png)
From the table:
![\sin ((7\pi)/(6))=\sin (210^o)=-(1)/(2)](https://img.qammunity.org/2023/formulas/mathematics/college/haxloh7qcgri2yunjgi1twzmjh3g5z6uyc.png)
8π/3 can be expressed as follows:
![(8)/(3)\pi=2\pi+(2)/(3)\pi](https://img.qammunity.org/2023/formulas/mathematics/college/os3u5djjga2nry7tsz5z8o9t51h1wcm9hl.png)
The function tan(x) is periodic, with a period of π. This means that evaluating:
![\tan ((8)/(3)\pi)](https://img.qammunity.org/2023/formulas/mathematics/college/v1ws69b4a42yu59neceobbvnedhhatrart.png)
is the same as evaluating:
![\tan ((2)/(3)\pi)](https://img.qammunity.org/2023/formulas/mathematics/college/w54qijvmppb9h84032czdomjth8hxkieam.png)
In this case, x (the input in the function) is translated 2π units to the left. From the periodicity of the function, the values are the same.
2π/3 radians is converted to degrees as follows:
![(2\pi)/(3)radians=(2\pi)/(3)radians\cdot\frac{180\text{ \degree}}{\pi\text{ radians}}=120\text{ \degree}](https://img.qammunity.org/2023/formulas/mathematics/college/78i4ney2xm6cyadg1s6anuu7999ja8rtd1.png)
From the table:
![\tan ((2)/(3)\pi)=\tan (120^o)=-\sqrt[]{3}](https://img.qammunity.org/2023/formulas/mathematics/college/989f5eh0n8104sxu1npfr7olsug3nfhj4a.png)
Substituting these values into the original expression:
![\begin{gathered} \sin ((7\pi)/(6))\cdot\tan ((8)/(3)\pi)= \\ =\sin ((7\pi)/(6))\cdot\tan ((2)/(3)\pi)= \\ =(-(1)/(2))\cdot(-\sqrt[]{3})= \\ =\frac{\sqrt[]{3}}{2} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/1hn1crbdifo2rc9wtbtsfonio4zbh8nn80.png)