听见
A:wear
B:hear
如图,在四棱锥A﹣BCDE中,底面BCDE是直角梯形,∠BED=90°,BE∥CD,AB=6,BC=5,CDBE=13,侧面ABE⊥底面BCDE,∠BAE=90°.
(1)求证:平面ADE⊥平面ABE;
(2)过点D作面α∥平面ABC,分别于BE,AE交于点F,G,求△DFG的面积.
计算下面各题,并用加法交换律验算.
tall he is now! But last year he was and thin.
红眼(R)雌果蝇和白眼(r)雄果蝇交配,F1代全是红眼,自交所得的F2代中红眼雌果蝇121头,红眼雄果蝇60头,白眼雌果蝇0头,白眼雄果蝇59头,则F2代卵细胞中具有R和r及精子中具有R和r的比例为( )