Question

OMG SOMEONE HELP ME PLEASE

Find the exact value of cos-1 sqrt3/2
pi/4
7pi/4
pi/6
11pi/6

I'm confused how to use the unit circle for this. I tried 180-120 which is 60 degrees and Idk what to do now..? Or should I subtract 180-60 to get 120?

Answer 1

Draw a Right Triangle.
Designate an acute angle.
Label it's adjacent side \(\sqrt{3}\)
Label the hypotenuse \(2\)
Ponder deeply!

Answer 2

Let x be the required angle,then
\[x=\cos^{-1} \frac{ \sqrt{3} }{ 2 } , or \cos x=\frac{ \sqrt{3} }{ 2 }=\cos \frac{ \pi }{ 6 },\cos \left( 2\pi-\frac{ \pi }{ 6 }\right)\]
\[x=\frac{ \pi }{ 6 },\frac{ 11\pi }{ 6 }\]

Answer 3

Oohh I get it now! Thanks!

Answer 4

yw

Answer 5

Except that 11pi/6 is not a solution. The argument is positive.