Trigo Application Urgent!~

1 ratio of area = (ratio of side)^2

Since ∆ ABC ~ ∆ DEA

area of ABC/area of DEA

= (BC/EA)^2

= 4

So, the area of ∆ ABC is 4 cm^2

2 As Q1, the area of ∆ BDE is 4/25*225 = 45 and the area of ∆ ADF is 9/25*225 = 81. So the area of parallelogram DECF is 225 - 45 - 81 = 99 cm^2

2011-05-11 21:08:55 補充：
Sorry,the area of ∆ BDE is 4/25*225 = 36