The rate of change of the function fix)-9 sec(x)+9 cos(x) is given by the expression 9 sec(x) tan(x) - 9 sin(x). Show that this expression can also be written as 9 sin(x) tan(x). Use the Reciprocal and Pythagor identities, and then simplify 9 sec(x) tan(x)-9 sin(x) = 9 sin(x) cos(x) cos(x) - 9 (sin(x)) -1)-