See Delta-time and framerate independence.
You don't need dt if you're just copying values, like setting one object's angle to another object's angle. You only need it when you increment frame-by-frame, such as moving an object to the right every frame, or rotating it a certain amount every frame. This includes rotating towards something: if you rotate 1 degree every frame, that will be 30 degrees/sec at 30 FPS and 60 degrees/sec at 60 FPS, which is framerate dependent; rotating by 60 * dt degrees will always be 60 degrees/sec at any framerate.