✔ 最佳答案
7.
∠YOX=90°(prop.of rhombus)
∴∠OXY=90°-40°(∠sum of ∆)
=50°
WZ//XY(prop.of rhombus)
∴b=50°(alt.∠s, WZ//XY)
∴C
8.
∠SOR=90°(prop.of rhombus)
∴6x+3x=90°(∠sum of ∆)
9x=90°
x=10°
3x=y(prop.of rhombus)
y=30°
6x=z(prop.of rhombus)
z=60°
∴B
9.
∠BDC=70°(prop.of rhombus)
CD=CB(def.of rhombus)
∴∠CBD=70°(base ∠s, isos.∆)
∴x=180°-70°-70°(∠sum of ∆)
=40°
∴A
10.
DI=IB(prop.of rectangle)
DB=AC(prop.of rectangle)
∴2(x-2)=6
x-2=3
x=5
∴C
11.
XS=XP(prop.of rectangle)
∠XSP=60°(base ∠s, isos.∆)
∴∠SXP=180°-60°-60°(∠sum of ∆)
=60°
∴SP=SX(side opp. eq.∠s)
=3cm
∴B
12.
ZX=√(12^2+5^2)(Pyth. theorem)
=13
∴IX=13/2(prop.of rectangle)
=6.5
∴A