Answer:
- [tex]\frac{2\sqrt{3} }{3}[/tex]
Step-by-step explanation:
Using the identity and the exact value
csc x = [tex]\frac{1}{sinx}[/tex] and sin60° = [tex]\frac{\sqrt{3} }{2}[/tex]
- 120° is in the third quadrant where sin < 0 , then
csc - 120° = - sin60° , then
csc - 120°
= [tex]\frac{1}{-sin60}[/tex]
= - [tex]\frac{1}{\frac{\sqrt{3} }{2} }[/tex]
= - [tex]\frac{2}{\sqrt{3} }[/tex] ( rationalise the denominator )
= - [tex]\frac{2}{\sqrt{3} }[/tex] × [tex]\frac{\sqrt{3} }{\sqrt{3} }[/tex]
= - [tex]\frac{2\sqrt{3} }{3}[/tex]
