等腰三角形PQR,PQ= PR= 3cm, QR=8cm,
两腰的和小于底明显有误数据有误拟PQ=PR=5cm
作△PRQ的高PH,则QH=8/2=4PQ=5
∴PH=3(勾股数)
(1)因为当0≤t≤4时,S=S△GCQ
∴当t=3时
QC=3GC/3=3/4GC=9/4
S=1/2•3•9/4=27/8((cm^2))
(2)因为当4≤t≤54时S=S△PQR-S△RG1C
∴当t=5时
G1C/3=RC/RH=(8-5)/4
∴G1C=9/4
S△RG1C=1/2•(8-5)•9/4=27/8
S△PRQ=1/2•3•8=12
∴S=12-27/8=69/8((cm^2))
(3)当5≤t≤8时S=S△ABC-S△RG1C-S△QG2B
QB=t-5QB/4=G2B/3
G2B=(3t-15)/4
∴S△QG2B=1/2•(t-5)•(3t-15)/4=3/8((t-5)^2)
RC=8-tRC/4=G1C/3
(8-t)/4=G1C/3⇒G1C=(24-3t)/4
S△RG1C=1/2•(8-t)•(24-3t)/4=3/8((8-t)^2)
S=12-3/8[((t-5)^2)+((8-t)^2)]