A: "A" equals left parenthesis, "f" Subscript, 1 , Baseline left parenthesis, "a" , right parenthesis , "f" Subscript, 2 , Baseline left parenthesis, "a" , right parenthesis , right parenthesisA=f1a,f2a
Label:
7
B: "B" equals left parenthesis, "f" Subscript, 2 , Baseline left parenthesis, "a" , right parenthesis , "f" Subscript, 4 , Baseline left parenthesis, "a" , right parenthesis , right parenthesisB=f2a,f4a
Label:
8
C: "C" equals left parenthesis, "f" Subscript, 4 , Baseline left parenthesis, "a" , right parenthesis , "f" Subscript, 3 , Baseline left parenthesis, "a" , right parenthesis , right parenthesisC=f4a,f3a
Label:
9
D: "D" equals left parenthesis, "f" Subscript, 3 , Baseline left parenthesis, "a" , right parenthesis , "f" Subscript, 1 , Baseline left parenthesis, "a" , right parenthesis , right parenthesisD=f3a,f1a
Label:
10
Expression 11: polygon left parenthesis, "A" , "B" , "C" , "D" , right parenthesispolygonA,B,C,D
11
a = ${a} "X" equals left parenthesis, "a" , 0 , right parenthesisX=a,0