过点A过垂线垂直于CD交CD于点E,则如题,AE长3cm,过点D做垂线垂直于AB交AB于F,则可知DF∥AE,DF=AE=3cm,
过点A做AG垂直于BC交BC于点G,如题,要求的是AG的长度,
AG=AB sin ∠ABG,
∠ABG=∠DAF,
sin∠DAF=DF/AD=3/4=0.75,
故AG=AB sin ∠ABG=5×0.75=3.75cm
过点A过垂线垂直于CD交CD于点E,则如题,AE长3cm,过点D做垂线垂直于AB交AB于F,则可知DF∥AE,DF=AE=3cm,
过点A做AG垂直于BC交BC于点G,如题,要求的是AG的长度,
AG=AB sin ∠ABG,
∠ABG=∠DAF,
sin∠DAF=DF/AD=3/4=0.75,
故AG=AB sin ∠ABG=5×0.75=3.75cm