A:2CH4(g)+4O2(g)═2CO2(g)+4H2O(l);△H═+890KJ/mol
B:CH4(g)+2O2(g)═CO2(g)+2H2O(l);△H═+890KJ/mol
C:CH4(g)+2O2(g)═CO2(g)+2H2O(l);△H═﹣890KJ/mol
D:2CH4(g)+4O2(g)═2CO2(g)+4H2O(l);△H═﹣890KJ/mol
“两岸猿声啼不住,轻舟已过万重山”描述的是( )
如图,AB为⊙O直径,E是BC中点,OE交BC于点D,BD=3,AB=10,则AC=____.
函数y=tan(π4﹣x)的定义域是____ .