國的肌何质( Properties of Plane Areas)國□ 矩形1A1=10×120=1200mm2 D=5mm 1=60mm 矩形2A2=10×80=800mm2 80 J2=10+ =50mm 2 2 =5mm O 所以p=41+A2 23mm 90 A1+A2 z1+ 2=38mm A1+A2(Properties of Plane Areas) 矩形 1 矩形 2 2 A1 = 10120 = 1200mm y1 = 5mm z1 = 60mm2 A2 = 1080 = 800mm 50mm 2 80 10 2 y = + = z 2 = 5mm 所以 38mm 23mm 1 2 1 1 2 2 1 2 1 1 2 2 = + + = = + + = A A A z A z z A A A y A y y 10 10 1 2 O z y 90 1 y 1z 2 z 2 y