Question

What is the exact value of cos 4/3 pi

Answer 1

no calculator?

Answer 2

-0.5

Answer 3

look at the x-value at \[\frac{ 4\pi }{ 3 }\]

Answer 4

0.999 or 1

Answer 5

You mean in Rad or Deg?
Rad :
\[\frac{4}{3}\times\pi=\pi+\frac{1}{2}\times\frac{2}{3} \times\pi\]
means
\[cos((\pi)+(\frac{\pi}{3}))=cos(\pi)cos(\frac{\pi}{3})-sin(\pi)sin(\frac{\pi}{3})\]
=
\[(-1\times0.5)-(0\times \frac{\sqrt{3}}{2}) \]

Answer 6

This is the first time I have used this site. I'm in my late 70's and foolishly said I'd help grandson with his maths. This is what I wanted to know. Thanks very much.

Answer 7

0.5

Answer 8

@HeilanGrannie it's my pleasure :)