2cos9/13πcosπ/13+cos5/13π+cos3/13π的解法?
来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/10/06 02:37:11
2cos9/13πcosπ/13+cos5/13π+cos3/13π的解法?
我有一个儿子,作为母亲的我无力解决,
我有一个儿子,作为母亲的我无力解决,
2cos9π/13cosπ/13+cos5π/13+cos3π/13(和差化积
)
=2cos9π/13cosπ/13+2 cos[(5π/13+3π/13)/2] cos[(5π/13-3π/13)/2]
=2cosπ/13(cos9π/13+cos4π/13)
=2cosπ/13[cos(π-4π/13)+cos4π/13]
=2cosπ/13[-cos4π/13)+cos4π/13]
=2cosπ/13*0
=0
)
=2cos9π/13cosπ/13+2 cos[(5π/13+3π/13)/2] cos[(5π/13-3π/13)/2]
=2cosπ/13(cos9π/13+cos4π/13)
=2cosπ/13[cos(π-4π/13)+cos4π/13]
=2cosπ/13[-cos4π/13)+cos4π/13]
=2cosπ/13*0
=0
计算cos5分之π+cos5分之2π+cos5分之3π+cos5分之4π
求值cos5π/8*cosπ8
求sin25π/6+cos5π/3+tan(-25π/4)+sin(-7π/3)×cos(-13π/6)-sin(-5π
信号与系统中,求cos2πt+cos3πt+cos5πt 角频率与周期
确定下列三角函数的符号 (1)sin156°:(2)cos5分之16π(3)cos(—450°)(
数学极限的运算lim α→π/2 (sinα-sin5α)/(cosα+cos5α)
cos5/12πcosπ/12+cosπ/12sinπ/6=?
求证cos2π/7+cosπ/3=cosπ/7+cos3π/7
cos方5π/12+cos方π/12+cosπ/12*cos5π/12 最后等于5/4的过程.
cos方5π/12+cos方π/12+cosπ/12*cos5π/12 最后等于4/5的过程.
(sin5π/12+cos5π/12)(sinπ/12-cosπ/12)
(sin5π/12-sinπ/12)(cos5π/12+cosπ/12)=?