15. The figure below shows that an image of Pac-Man forms a central angle of 0 in a circle x with radius r units inscribed in a square with the length side of x units. Assuming that the arc length of the O subtended sector is units and the following co- 11 function identity is true for all values of x > o , find the exact value of the central angle 0. 60T 11 csc (-3x3 - 21X - 80 ) = sec 4x3 - 37X - 97X+ 2