Question

How do you find cos(11pi/6)?

Answer 1

HI!!

Answer 2

you need a good trig cheat sheet !

Answer 3

hint:
we have:
\[\Large \frac{{11\pi }}{6} = 2\pi - \frac{\pi }{6}\]

Answer 4

so we can write:
\[\Large \cos \left( {\frac{{11\pi }}{6}} \right) = \cos \left( {2\pi - \frac{\pi }{6}} \right)\]

Answer 5

find \(\frac{11\pi}{6}\) on the unit circle on the the last page of the cheat sheet, then look at the coordinates of the corresponding point
the first coordinate is cosine

Answer 6

Thanks guys

Answer 7

\[\color\magenta\heartsuit\]

Answer 8

What if you need to find tangent?

Answer 9

you can apply this identity:
\[\Large \begin{gathered}
\tan \left( {\frac{{11\pi }}{6}} \right) = \tan \left( {2\pi - \frac{\pi }{6}} \right) = \hfill \\
\hfill \\
= \frac{{\tan \left( {2\pi } \right) - \tan \left( {\frac{\pi }{6}} \right)}}{{1 + \tan \left( {2\pi } \right)\tan \left( {\frac{\pi }{6}} \right)}} \hfill \\
\end{gathered} \]

Answer 10

How do you know tan(11pi/6) equals tan(2pi-pi/6)?