∴∠CDB = 30°, that is, the slope angle of the new slope surface is 30;
(2)∫CBBD = 33，BC= 12
∴DB=3BC= 123，
In Rt△ABC, tan∠CAB=CBBA= 1
∴ab=bc= 12, 12-( 123- 12)=24- 123≈3.24