Question

How do you evaluate `cos^-1(cos((-2pi)/3))`?

Answer 1

Value of `cos^(−1)(cos(−2π/3))` is `−2π/3`.

Explanation:

The value of function `cos^(−1) x` is equal to the value of the angle whose cosine is `x`.

Assume `x=cos (−2π/3)`.

Finding the value of `cos^(−1)(cos(−2π/3))` means finding the value of `cos^(−1)x`

But if `x=cos (−2π/3)`, obviously `cos^(−1)x=(−2π/3)`

Hence value of `cos^(−1)(cos(−2π/3))` is `−2π/3`.