∵a⊥b,∴a•b=0,即1×2+2x+3×4=0,解得x=-7.
故答案为-7.
在Rt△ABC中,∠C=90°,AB=5,AC=4,则sinA的值为______.
A number of sheep _________ seen by us when we passed the field..
A.is
B.are
C.was
D.were