若角α的终边与直线y=3x重合且sinα<0,又P(m,n)是α终边上一点,且|OP|=,则m-n等于( )A.2 B.-2 C.4 D.-4 答案:解析:因为sinα<0,所以角α的终边在第三或第四象限或y轴的非正半轴上.而y=3x经过原点在第一象限和第三象限内,且角α的终边与y=3x重合,所以角α的终边在第三象限,可得m<0,n<0.又因为P(m,n)在直线y=3x上,所以满足n=3m.同时|OP|=,可得m2+n2=10,即解得或所以m-n=-1-(-3)=2.答案:AEvery great culture in the past had its own
ideas of beauty in art and literature.
A. expressed
B. to express
C. being expressed
D. to be expressed