The function f(theta) and g(theta) are sine functions where f(0) = g(0) = 0. The amplitude of f(theta) is twice the amplitude of g(theta). The period of f(theta) is one-half the period of g(theta). If g(theta) has a period of 2x, and f(pi/4) = 4, write the function rule for g(theta). Explain your reasoning.