Prove Quatrilateral

長方形
prop. of //gram
equal diagonals

菱形
prop. of //gram
diagonals bisect interiop angles
diagonals perpendicular

正方形
長方形&菱形的reason都岩用...

prop. of //gram 係平行四邊形
但係唔可以咁寫...要寫明邊個reason
因為平行四邊形的reason有3個
opp. sides equal
opp. angles of//gram
diag. of //gram