如图△ABC中,AC=14cm,DE为AB的垂直平分线,△ACD的周长为26cm,则BC的长( )。
12cm
在图示变截面杆中,AB段、BC段的轴力为()。
A.NAB=-10kN,NBC=4kN
B.NAB=6kN,NBC=4kN
C.NAB=-6kN,NBC=4kN
D.NAB=10kN,NBC=4kN
An infinite sequence of positive integers is called an "alpha sequence" if the number of even integers in the sequence is finite. If S is an infinite sequence of positive integers, is S an alpha sequence ?() (1)The first ten integers in S are even. (2)An infinite number of integers in S are Odd.
A.条件(1)充分,但条件(2)不充分.
B.条件(2)充分,但条件(1)不充分.
C.条件(1)和(2)单独都不充分,但条件(1)和条件(2)联合起来充分.
D.条件(1)充分,条件(2)也充分.
E.条件(1)和条件(2)单独都不充分,条件(1)和条件(2)联合起来也不充分.