運算式 2: "P" Subscript, "y" , Baseline left parenthesis, "t" , right parenthesis equals sine left parenthesis, "t" , right parenthesisPyt=sint
2
運算式 3: left parenthesis, "P" Subscript, "x" , Baseline left parenthesis, "t" , right parenthesis , "P" Subscript, "y" , Baseline left parenthesis, "t" , right parenthesis , right parenthesisPxt,Pyt