已知△ABC的三个内角为A，B，C，向量m=（cosA，-sinB），n=（cosB，sinA）满足m·n=cosC． （Ⅰ）求证：△ABC是直角三角形； （Ⅱ）若AC=，BC=6，P是△ABC内的一
如图10所示，物体甲的长度为 cm，停表乙的示数为 s。
已知线段a,b,c,求作a,b,c的第四比例项x..
为贯彻落实民族区域自治法，1949年《共同纲领》明确确定“各少数民族聚居的地区，实行民族区域自治；1954年将民族区域自治制度载入宪法；1984年颁
Some women a good salary in a job instead of staying home, but they decided not to work for the sake of the family. A. could have made B. should have made C. would make D. must mak
When students and parents are asked to rate subjects according to their importance, the arts are unavoidably at the bottom of the list. Music is nice, people seem to say, but not important. Too often
词汇：根据句意及首字母或中文提示，完成下列单词的拼写 1. Eating too much and doing little exercise makes us u__________________. 2. It's very important for the students to k
下图反映的是哪一时期的边境贸易? （ ） A．东晋 B．南朝 C．北宋
的图像在点
的处的切线过点
，则 
.