According to the S-section rectangle ABCD = s+s△BOC-s sector BOC, the length and width of the rectangle, the bottom and height of the equilateral △BOC, the radius and radian of the sector BOC are calculated respectively, and then solved according to the area formula: OE⊥BC with the intersection o as point E,
∵OB=OC,OE⊥BC，
∴∠BOE=？ ∠BOC= 1/2？ ×60 =30 ,
∴BE=？ OB=？ × 10 = 5mm；
In Rt△OEB, the root number of OE=5 is 3(mm).
OB = OC，∠BOC=60，
∴△BOC is an equilateral triangle, ∴BC=OB= 10(mm).
∴S section =S rectangular ABCD+S△BOC+S sector BOC=25× 10+? 1/2* 10×5 radical 3-1/6 * 3.14 *10 *10? ≈250+43.3-52.3=24 1(mm2)。