Question

find the value of cos (-870)​

Answer 1

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Answer 2

The required value of $\cos (-870)$ is $=\frac{\sqrt{3}}{2}$.

Step-by-step explanation:

Consider the provided information.

We need to find the value of $\cos (-870)$

$\cos (-870) = \cos 870$    (∴cos(-θ)=cosθ)    

$=-\cos (900-30)$

$=-\cos(5\pi-\frac{\pi}{6})$

$=-\cos(-\frac{\pi}{6})$        (∴cos(-θ)=cosθ)  

$=\frac{\sqrt{3}}{2}$

Hence, the required value of $\cos (-870)$ is $=\frac{\sqrt{3}}{2}$.

#Learn more

Prove that sin square A cos square B - cos square A sin square B = sin square A - sin square B

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