Answer:
The inverse cosine of cosine is the angle contained in the cosine, i.e
[tex]\cos ^{-1}(\cos \theta)=\theta[/tex]
therefore, to find the value of cos^-1 (cos 7 pi /5 ), we just extract 7 pi /5 and we have our answer.
2.
The inverse function
[tex]\cos ^{-1}\frac{11}{3}[/tex]
give us back the angle that its cosine is 11/3. However, we have to remember that since cosine is the ratio between adjacent and hypotenuse, it is always less than zero; therefore, 11/3 is not a cosine ratio since it is greater than 1 and thereofre, cos^-1 11/3 is undefined and so is cos (cos^-1 (11/3))
