作业帮问大家一道关于三角函数的题目
来源：学生作业帮 编辑：作业帮 分类：数学作业 时间：2024/05/13 04:58:41
问大家一道关于三角函数的题目
我要问的是第二道,
我要问的是第二道,
sin99°=cos9°
sin(-1071°)=sin(-1080°+9°)=sin9°
cot(-1089°)=-cot(1080°+9°)=-cot9°
cot(-630)=cot(-720°+90°)=cot90°=0
sin(-171°)=-sin171°=-sin(180°-9°)=-sin9°
sin(-261°)=sin(-270°+9°)=cos9°
sin(-1071)sin99+sin(-171)(sin-261)+cot(-1089)cot(-630)
=sin9cos9+(-sin9)cos9-cot9*0
=0
sin(-1071°)=sin(-1080°+9°)=sin9°
cot(-1089°)=-cot(1080°+9°)=-cot9°
cot(-630)=cot(-720°+90°)=cot90°=0
sin(-171°)=-sin171°=-sin(180°-9°)=-sin9°
sin(-261°)=sin(-270°+9°)=cos9°
sin(-1071)sin99+sin(-171)(sin-261)+cot(-1089)cot(-630)
=sin9cos9+(-sin9)cos9-cot9*0
=0