A:have polluted
B:is being polluted
C:has been polluted
D:have been polluted
A、B、C、D是同一球面上的四个点,其中△ABC是正三角形,AD⊥平面ABC,AD=4,AB=23,则该球的表面积为____
若α为锐角,且sinα=45,则tanα为( )