表达式2: "P" Subscript, "y" , Baseline left parenthesis, "t" , right parenthesis equals sine left parenthesis, "t" , right parenthesisPyt=sint
2
表达式3: left parenthesis, "P" Subscript, "x" , Baseline left parenthesis, "t" , right parenthesis , "P" Subscript, "y" , Baseline left parenthesis, "t" , right parenthesis , right parenthesisPxt,Pyt
定义域t最小值: 00
less than or equal to "t" less than or equal to≤t≤