Final answer:
The maximum value of the function y=1+3sinx is 4, which occurs when sinx is at its maximum value of 1.
Step-by-step explanation:
The maximum value for the function y=1+3sinx is determined by the maximum value that the sine function can take, which is 1. Since the sine function oscillates between -1 and +1, the amplitude of the sine function has the greatest impact on the maximum value of the entire function. In this case, the amplitude is 3. Therefore, the maximum value of the function is y = 1 + 3(1) = 4. This value occurs when sinx is at its maximum, which is when x corresponds to the angle where the sine function equals 1.