Corresponding sides are a pair of matching sides in two different shapes (size does not matter). In the field of geometry, the concept of corresponding sides plays an important role to prove various triangular theorems.
The Boeing B-17 Flying Fortress is a four-engine heavy bomber aircraft developed in the 1930s for the United States Army Air Corps (USAAC).
Fortress. a strategically important point (or city) with a permanent garrison, armament, supplies, and independent headquarters, which is prepared for perimeter defense by means of permanent fortification and the provision of everything necessary for prolonged battle under siege conditions.he fortress castle was the residence of the feudal lord and the place where he stationed his armed detachment, whose function was to hold the population of the subordinate areas and cities in submission and wage combat against neighbors.