If cos^-1 x = 2π/3, what is x?

Inverse Trigonometric Functions · Question 33 of 120

Question 33

EasyOriginal question

If $\cos^{-1} x = \frac{2\pi}{3}$ , what is $x$ ?

- \frac{\sqrt{3}}{2}

Correct answerYour answer

- \frac{1}{2}

Correct answerYour answer

\frac{1}{2}

Correct answerYour answer

\frac{\sqrt{3}}{2}

Correct answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer B

Correct answer: B

$\cos^{-1} x = \frac{2\pi}{3}$ means $x = \cos \frac{2\pi}{3}$ , and $\frac{2\pi}{3}$ is on the branch.
$\cos \frac{2\pi}{3} = -\frac{1}{2}$ .

Worth noting

$\frac{1}{2}$ is $\cos \frac{\pi}{3}$ ; an angle past $\frac{\pi}{2}$ has a negative cosine.

Ten questions from Inverse Trigonometric Functions, at your own pace.

Ten questions from Inverse Trigonometric Functions, at your own pace.