解:
过P作PM⊥BC于M .
Rt△BPM中,sin∠B=PM/PB
∴PM=PB•sin∠B= (4-t )sin60º= (4-t )• √3/2.
∴S△PBQ= BQ•PM= t (4-t )• √3/2
∴
y=S△ABC-S△PBQ
=½AB• BCsin60º-S△PBQ
=½ ×4×4x √3/2-t (4-t )• √3/2
= 4√3- (4t-t² )• √3/2
∴y与t的关系式为: y=4√3- (4t-t² )• √3/2 (0≤t≤4)