Based on your question that ask to graph the following function an the best answer is this one:
To find the max/min, you basically have to equate the first derivative to zero. that will give you a value of "x". now after having done that, find the second derivative. if it is grater than zero, it will have min. value, if it is less than zero, it will have max. value
Then x= 3pi/4 and 7pi/4