The parameter equation is x = cost, y = Sint, 0 ″ t ″ 2pi x=cost,y=sint,0《t《2pi The book says it's a circle, but I think it's a circle Why does t have to move on a circle if t is a straight line?

The parameter equation is x = cost, y = Sint, 0 ″ t ″ 2pi x=cost,y=sint,0《t《2pi The book says it's a circle, but I think it's a circle Why does t have to move on a circle if t is a straight line?

Straight line motion shows that you are at the top of a corner. It can't be a straight line. How can y = Tan t be a straight line? When you see this kind of condition in the future, you should immediately respond. What kind of figure is this trajectory, and this condition meets the condition of circle, so it is a circle. In the future, you should also encounter the problems of ellipse, hyperbola, parabola and so on. You should pay attention to induction and practice more