已知 cos π/5 =(根号5 +1)/4 求 sin π/5,sin -π/5 ,sin 4π/5 ,sin 3π/10cos π/5,cos -π/5 ,cos 4π/5 ,cos 3π/10 如果有空顺便做下这个呗.
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![已知 cos π/5 =(根号5 +1)/4 求 sin π/5,sin -π/5 ,sin 4π/5 ,sin 3π/10cos π/5,cos -π/5 ,cos 4π/5 ,cos 3π/10 如果有空顺便做下这个呗.](/uploads/image/z/5257714-58-4.jpg?t=%E5%B7%B2%E7%9F%A5+cos+%CF%80%2F5+%3D%28%E6%A0%B9%E5%8F%B75+%2B1%EF%BC%89%2F4+%E6%B1%82+sin+%CF%80%2F5%2Csin+-%CF%80%2F5+%2Csin+4%CF%80%2F5+%2Csin+3%CF%80%2F10cos+%CF%80%2F5%2Ccos+-%CF%80%2F5+%2Ccos+4%CF%80%2F5+%2Ccos+3%CF%80%2F10+%E5%A6%82%E6%9E%9C%E6%9C%89%E7%A9%BA%E9%A1%BA%E4%BE%BF%E5%81%9A%E4%B8%8B%E8%BF%99%E4%B8%AA%E5%91%97.)
已知 cos π/5 =(根号5 +1)/4 求 sin π/5,sin -π/5 ,sin 4π/5 ,sin 3π/10cos π/5,cos -π/5 ,cos 4π/5 ,cos 3π/10 如果有空顺便做下这个呗.
已知 cos π/5 =(根号5 +1)/4 求 sin π/5,sin -π/5 ,sin 4π/5 ,sin 3π/10
cos π/5,cos -π/5 ,cos 4π/5 ,cos 3π/10 如果有空顺便做下这个呗.
已知 cos π/5 =(根号5 +1)/4 求 sin π/5,sin -π/5 ,sin 4π/5 ,sin 3π/10cos π/5,cos -π/5 ,cos 4π/5 ,cos 3π/10 如果有空顺便做下这个呗.
cosπ/5=sinπ/5=x/r=(根号5 +1)/4 则y=√4²-√5+1=2√5
sinπ/5=cosπ/5=y/r=2√5/4=√5/2
sin-π/5=cosπ/5=-y/r=-√5/2
sin4π/5=cos4π/5=y/r=√5/2
sin3π/5=cos3π/5=y/r=√5/2 注:是2分之根5
cos-π/5=sinπ/5=x/r=√6/4
cos4π/5=sin4π/5=-√6/4
cos3π/10=sin3π/10=√6/4 注:是4分之根6
cos π/5你题目有的
原理:诱导公式
用诱导公式呗。。
1
sin36≈0.5878 sin-36≈-0.5878 sin 4π/5=sin π/5≈0.5878
sin 3π/10≈0.809
cos -π/5=cos π/5 =(根号5 +1)/4
cos 4π/5=-cos π/5=-【(根号5 +1)/4】
cos54=0.5878
要过程的话可以给你!