做法一:
连接AC
AC//FG
所以S△FGA = S△FGC = b²/2
做法二:
S△FGA = ABCD + FCGE - S△ABG - S△ADF - S△EFG
= a² + b² - (a+b)a/2 - (a-b)a/2 - b²/2
= b²/2
做法一:
连接AC
AC//FG
所以S△FGA = S△FGC = b²/2
做法二:
S△FGA = ABCD + FCGE - S△ABG - S△ADF - S△EFG
= a² + b² - (a+b)a/2 - (a-b)a/2 - b²/2
= b²/2