The function below models the voltage, in volts, of a certain alternating-current circuit after x seconds, where a and b are positive constants. f(x)=acos(bx) assume the expression inside the cosine function is measured in radians. what is the largest value of c such that when the voltage function's domain is restricted to the interval [0,c] , the function is invertible? use the on-screen keyboard to type the answer in the box below.