A:CH3COOH
B:HNO3
C:C17H35COOH
D:CH3OH
165-35-65
It was sunny.I can go c____.
如图,在等腰直角三角形ABC中,∠ACB=90°,AB=42.以A为圆心,AC长为半径作弧,交AB于点D,则图中阴影部分的面积是 ____ .(结果保留π)