2.B【解析】法:z=6+8i(6+8i)(1-3i)3+434-331+3i42+2i,所以z=2+4-3323+432=5.2法二:z=6+8i16+8il101+3i1+3i2=3.B【解析】k=tan=3,cos=110n10,所以sin20=2sincos=53√101+tan210