As shown in figure (1), the straight line y=kx+ 1 intersects with the positive semi-axis of Y axis A and with the positive semi-axis of X axis B, making a square ABCD with AB as the side. (1) If C(3,

As shown in figure (1), the straight line y=kx+ 1 intersects with the positive semi-axis of Y axis A and with the positive semi-axis of X axis B, making a square ABCD with AB as the side. (1) If C(3, m), Let the CE⊥x axis be at point e,

Yi Zheng △ OAB △ EBC,

∴OB=OE-BE=3-OA=2，

∴CE=2, that is, m = 2；;

(2) Let the GE⊥x axis be at the G point,

BE = BF，

∴∠ 1=∠2,

∠∠2 =∠MFC，∠MFC+∠3=90，∠4+∠ 1=90

∴∠3=∠4,

∴EG=GB，

AE=2EB，

∴AC=2AB，

∫AE+EB = AB，

∴AE=(2-2)AB，

∴ac+ae=2ab；

(3) Connect ct, ST and ST to BC in M,

Then AS=TS, SC=SM, ∠ sta = 45,

∴AS-CS=MT，

∴as-csbt= 1btmt= 1cos45 = 2。

Therefore, the value of AS-CSBT remains unchanged.