A:两个原子之间的相互作用叫化学键
B:共价化合物中只含有共价键
C:离子化合物中只含有离子键
D:完全由非金属元素形成的化合物一定是共价化合物
已知sin(π2+α)=13,则cos(π+α)的值为____
—Of course they were. You know, Spiderman was always those boys' favourite.