— Can I bring a friend to your birthday party?
—Sure, ________.
A:no problem
B:not at all
C:my pleasure
D:well done
已知f(x)在R上是奇函数,且f(x+2)=﹣f(x),当x∈(0,2)时,f(x)=2x2,求f(2015).
当锐角α>30°时,cosα的值是( )