When you plugged this into your calculator (in "radian"
mode), what did you get? You plugged [tex]-\frac{13}{14}\pi[/tex] in for "x" in the inner cosine:
. . . . .[tex]7\, \left(-\dfrac{13}{14}\pi\right)\, =\, -\dfrac{13}{2}\pi[/tex]
. . . . .[tex]-\dfrac{13}{2}\pi\, =\, -\dfrac{16}{2}\pi\, +\, \dfrac{3}{2}\pi\, =\, -8\pi\, +\, \dfrac{3}{2}\pi[/tex]
. . . . .[tex]\cos\left(-\dfrac{13}{2}\pi \right)\, =\, \cos\left(\dfrac{3}{2}\pi \right)\, =\, ...?[/tex]
You plugged this result into the argument for the outer cosine, and got... what? Then you evaluated the outer cosine at this value and got... what? How did you arrive at "1"?
Please be complete. Thank you!
Bookmarks