Question

Cos 20pi/3

Answer 1

try it on a calculator in radian mode?

Answer 2

Do you mean \[\cos(20) \times (\pi/3)\]?

Answer 3

I'm assuming that's the correct equation. Parenthesis are very important in an equation.

The solution is \[\frac{ 1 }{ 3 } \pi \cos(20)\]

Answer 4

\[\cos\left(\frac{20\pi}{3}\right)=\cos\left(6\pi+\frac{2\pi}3\right)=\cos\left(\frac{2\pi}3\right)\]