Answer:
- 1
Step-by-step explanation:
Using the trigonometric identity
cos(- x) = cosx and exact value cos60° = [tex]\frac{1}{2}[/tex]
Given
f(x) = - 2cosx , then
f(- 300° )
= - 2cos(- 300)°
= - 2cos(300)°
= - 2cos(360 - 300)°
= - 2cos60°
= - 2 × [tex]\frac{1}{2}[/tex]
= - 1
