表达式16: "y" less than "l" left parenthesis, "x" , right parenthesis left brace, "r" Subscript, "x" , Baseline greater than or equal to "x" greater than 0 , right brace left brace, "y" greater than 0 , right bracey<lxrx≥x>0y>0
16
表达式17: "y" less than "f" left parenthesis, "x" , right parenthesis left brace, "x" greater than "r" Subscript, "x" , Baseline , right brace left brace, "y" greater than 0 , right bracey<fxx>rxy>0
17
表达式18: "A" Subscript, "p" "i" "e" , Baseline equals Start integral from 0 to "a" Subscript, "x" , Baseline , end integral, "f" left parenthesis, "x" , right parenthesis "d" "x"Apie=∫ax0fxdx
18
表达式19: "A" Subscript, "g" "r" "e" "e" "n" , Baseline equals Start integral from 0 to "r" Subscript, "x" , Baseline , end integral, "l" left parenthesis, "x" , right parenthesis "d" "x" positive Start integral from "r" Subscript, "x" , Baseline to "a" Subscript, "x" , Baseline , end integral, "f" left parenthesis, "x" , right parenthesis "d" "x"Agreen=∫rx0lxdx+∫axrxfxdx
19
表达式20: "A" Subscript, "r" "e" "s" "t" , Baseline equals "A" Subscript, "p" "i" "e" , Baseline minus "A" Subscript, "g" "r" "e" "e" "n" , BaselineArest=Apie−Agreen
