"You will take that class."
Translation:Usted va a tomar esa clase.
The imperative isn't actually about orders, it is about the way you address a person or group. The phrase "You will take that class" is describing/indicating to the person (you) what will happen. The imperative form would be "Take that class". You are not talking about the event, you are directly telling, or suggesting to the person to participate. The imperative can be very polite. For example "Enjoy your meal" is imperative while "You will enjoy your meal" is indicative.