(1) ∵ tangent semicircle o of CD at point e.

∴OE⊥CD( 1)，

∵BD is the hypotenuse △BCD of an isosceles right angle,

∴BC⊥CD,∠CDB=∠CBD=45，

∴OE∥BC(2 o'clock),

∴∠ABC=∠AOE=60，

∴∠ ABG =∠ ABC-∠ CBD = 60-45 =15, (3 points)

∴ The reading of protractor at G point α = radian AG = 2∠ ABG = 30, (4 points)

(2)OF = OB = 12AB = 4cm，∠ABC=60，

∴△OBF is a regular triangle, ∠ BOF = 60, (5 points)

∴S sector OBF= 16×42? π= 83π(cm2)(6 points)

S△OBF=34×42=43 (square centimeter) (7 points)

∴S shadow =S sector OBF-S△OBF=(83π-43)cm2

∴ Shadow area is (83π-43)cm2(8 points).