Question

If cos of theta= -(1/6), what is the cos(-10pi-theta)?
How can i solve this question?

Answer 1

-(1/6).

Explanation:

The angle whose cosine is -1/6 can be written as arccos(-1/6).

cos (-1/6) = cos (-2npi - arccos(-1/6) where n is an integer. The terminal angles are the same. When n = 5 we have cos(-10pi - arccos(-1/6).

So cos (-1/6) = cos(-10pi - arccos(-1/6))

and therefore cos (-10pi - arccos(-1/6) = -1/6.

We can confirm this by using a scientific calculator.