英文正方形數學題(20分)

!!!長方形的兩條對角線相等且
互相平分!!!
1. AD=AE (菱形的邊)
=DE=BD/2
=7.5 cm

2. because EG=GD(=AD)=DE
so, Angle EDG = 60° (等邊三角形)
sin(angle FDE)=BC/BD
=AD/2DE (長方形對邊)
=AD/2AD (DE=AD)
=1/2
angle FDE= arcsin 1/2
=30°
Therefore, angle FDG=(angle EDG)-(angle FDE)
=60°-30°
=30°

2009-02-01 15:24:56 補充：
"&deg" means degrees

正方形 square