已知点O为△ABC的外心,若∠A=80°,则∠BOC的度数为( )
如图是某几何体的三视图,其中正视图是腰长为2的等腰三角形,俯视图是半径为1的半圆,则该几何体的体积是( )
——My best friend is more popular than me. I want to be like him.——I think you should be more friendly,