A:My sister is very old.
B:My brother is very young.
C:My sister is very young.
请结合图表完成下列各题:
草履虫在显微镜下有时会呈现绿色,这是因为( )
(Ⅰ)求∠A的大小;
(Ⅱ)若a= 3 ,且sinA+sin(B﹣C)=2sin2C,求△ABC的面积.