Equilateral pentagon of δ can be seen from the figure: Simplifying, δ is obtained as function of α and β: The remaining angles of the pentagon can be found geometrically: The remaining angles of the orange and blue triangles are readily found by noting that two angles of an isosceles triangle are equal while all three angles sum to 180°. Then formula_7 and the two remaining angles of the green triangle can be found from four equations stating that the sum of the angles of the pentagon is 540°, the sum of the angles of the green triangle is 180°, the angle
The Pentagon and most of the design work completed by June 1, 1942. At times the construction work got ahead of the design, with different materials used than specified in the plans. Pressure to speed up design and construction intensified after the attack on Pearl Harbor on December 7, 1941, with Somervell demanding that of space at the Pentagon be available for occupation by April 1, 1943. David J. Witmer replaced Bergstrom as chief architect on April 11 after Bergstorm resigned due to charges, unrelated to the Pentagon project, of improper conduct while he was president of the American Institute of Architects.