In ladder ABCD, ad ‖ BC (AD

In ladder ABCD, ad ‖ BC (AD

In ladder ABCD, the area of ∵ ad ∥ BC, ∥ abd is equal to that of ∥ ACD, and then the area of ∥ AOB is equal to that of ∥ cod. Note that the area of these two triangles is S1, the area of ∥ AOD is S2, the area of ∥ BOC is S3, and the total area of ladder is s. let ad = a, BC = B