sin21°cos81°+cos189°sin69°化简

来源：学生作业帮编辑：大师作文网作业帮分类：数学作业时间：2024/11/13 15:02:34

sin21°cos81°+cos189°sin69°
=sin21°cos81°-cos9°sin69°
=sin21°sin9°-cos9°cos21°
=-cos(9+21)°
=-cos30°
=-√3/2

计算：sin21°+sin22°+sin23°+…+sin287°+sin288°+sin289°．计算：sin21°+sin22°+sin23°+…+sin288°+sin289°+sin290°= ___ ． 1.比大小：tan21°和tan31°；2.sin21°和cos21°；3.cos21°和cos22° 至少需要几颗同步卫星才能"覆盖"整个地球赤道(已知地球半径6400km ,取g=10m/s2,cos81.3=0.15）不求值,分别比较下列各组中两个三角函数值的大小(1)sin21/5π与sin42/5π sin1/5与cos5 化简sin12°×sin48°×sin54°? 化简：cos10°tan20° 化简COS8°-SIN17°SIN9°/COS9° 化简 cos15°cos45°-cos75°sin45° 化简：sin48°×sin57°—sin42°sin33° 化简sin6°cos24°sin78°cos48° 化简(tan53°-cot67°)/(1+tan53°tan23°)