See screenshot below

Answer:
cos theta = -1/ 2
Step-by-step explanation:
sin theta = -sqrt(3)/2
Drawing a triangle
We know sin theta = opp/hyp
We can determine the adj side using the Pythagorean theorem
a^2 + b^2 = c^2
adj^2 + (-sqrt(3))^2 = 2^2
adj^2 +3 = 4
adj^2 = 4-3
adj ^2 =1
Taking the square root of each side
adj = 1
We know that since it is in the third quadrant the adj side is negative
adj = -1
cos theta = adj / hyp
cos theta = -1/ 2
Answer:
Solution given:
Sin[tex]\theta_{1}=\frac{-\sqrt{3}}{2}[/tex]
[tex]\frac{opposite}{hypotenuse}=\frac{-\sqrt{3}}{2}[/tex]
equating corresponding value
opposite=-[tex]\sqrt{3}[/tex]
hypoyenuse=2
adjacent=x
By using Pythagoras law
hypotenuse²=opposite²+adjacent²
2²=-[tex]\sqrt{3²}[/tex]+x²
4=3+x²
x²=4-3
x=[tex]\sqrt{1}=1[/tex]
x=-1
In third quadrant
Cos angle is negative
Cos[tex]\theta_{1}=\frac{-adjacent}{hypotenuse}[/tex]