三角函数简单计算(cos36度)^2+(sin18度)^2的值
2019-05-27
三角函数简单计算
(cos36度)^2+(sin18度)^2的值
优质解答
(sin18)^2+(cos36)^2
=(1-cos36)/2+(1+cos72)/2
=1+(cos72-cos36)/2
=1-sin18sis54
=1-cos36cos72
=1-sis72/(2sin36)*sin144/(2sin72)
=1-sin36/(4sin144)
=1-sin36/(4sin36)
=1-1/4=3/4
(sin18)^2+(cos36)^2
=(1-cos36)/2+(1+cos72)/2
=1+(cos72-cos36)/2
=1-sin18sis54
=1-cos36cos72
=1-sis72/(2sin36)*sin144/(2sin72)
=1-sin36/(4sin144)
=1-sin36/(4sin36)
=1-1/4=3/4