MHB So the exact value of Cos(-pi/3) is 1/2.

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The exact value of Cos(-π/3) is 1/2, as cosine is an even function, meaning Cos(-θ) equals Cos(θ). The unit circle coordinates for -π/3 are (1/2, -√3/2), where the x-value represents the cosine. It is clarified that the cosine value does not become the inverse when dealing with negative angles. Therefore, Cos(-π/3) is correctly identified as 1/2.
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Hello!
Simple as it sounds, I would greatly appreciate help on finding the exact value of Cos(\frac{-\pi}{3}
If I need to find a negative value of Cos, does it become the inverse?
So, since if I draw on unit circle, I get (\frac{\sqrt{3}}{2}, \frac{-1}{2}), would the value of Cos(-pi/3) = the y-value of -1/2?
Thank you!
 
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riri said:
Hello!
Simple as it sounds, I would greatly appreciate help on finding the exact value of Cos(\frac{-\pi}{3}
If I need to find a negative value of Cos, does it become the inverse?
So, since if I draw on unit circle, I get (\frac{\sqrt{3}}{2}, \frac{-1}{2}), would the value of Cos(-pi/3) = the y-value of -1/2?
Thank you!

No. you should get $(\frac{1}{2}, \frac{-\sqrt{3}}{2})$ and you should take the x value as $\cos = \frac{x}{hypotenuse }$ and value of cos is x as hypotenuse is 1
 
riri said:
Hello!
Simple as it sounds, I would greatly appreciate help on finding the exact value of Cos(\frac{-\pi}{3}
If I need to find a negative value of Cos, does it become the inverse?
So, since if I draw on unit circle, I get (\frac{\sqrt{3}}{2}, \frac{-1}{2}), would the value of Cos(-pi/3) = the y-value of -1/2?
Thank you!

You could also use the fact that cosine is an even function, that is $\cos(-\theta)=\cos(\theta)$ to write:

$$\cos\left(-\frac{\pi}{3}\right)=\cos\left(\frac{\pi}{3}\right)=\frac{1}{2}$$
 
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