Plane geometric photography theorem

Solution: As we all know, in plane geometry,

If in △ABC, AB⊥AC, AE⊥BC and E are vertical rulers.

So AB2=BD? BC,

We can analogize this property and infer that:

If in the triangular pyramid A-BCD, the AD⊥ plane ABC, the AO⊥ plane BCD and O are vertical feet.

Then (s △ ABC) 2 = s △ BOC. s △ BDC。

So the answer is: (s △ ABC) 2 = s △ BOC. s △ BDC。