I sent a big bunch of flowers to the nurse as an ________ of thanks for her taking good care of my grandpa in the nursing home. ( )
图(a) 图(b)
以直角坐标系的原点为极点,x轴的非负半轴为极轴,并在两种坐标系中取相同的长度单位,点M的极坐标是4,2π3,则点M直角坐标是( )