=(2sinπ/5cosπ/5cos2π/5)/2sinπ/5
=(sin2π/5cos2π/5)/2sinπ/5
=(2sin2π/5cos2π/5)/4sinπ/5
=sin4π/5/4sinπ/5
=sin(π-π/5)/4sinπ/5
=sinπ/5/4sinπ/5
=1/4
COS(PAI/5)COS(2PAI/5)=?
2个回答
相关问题
-
cos(pai/5+2)cos(pai/5-2)=?A.cos^2pai/5+sin平方2 B.sin^2pai/5-c
-
cos(pai/5)cos((2/5) pai)的值是～
-
证明cos(pai/7)+cos(pai*3/7)+cos(pai*5/7)=0.5
-
[cos(a-pai/2)]/[sin(5pai/2+a)]*sin(a-2pai)cos(2pai-a)=
-
cos (a+4pai)cos ^2(a+pai)sin^2(a+3pai)/ sin(a-4pai)sin(5pai+
-
cos(a+b)=3/5 sin(b-pai/4)=5/13 a,b 属于(0,pai/2) 求cos(a+pai/4)
-
Sin(pai-x)cos(2pai-x)tan(pai+x)+cos(pai-x)^2
-
三角函数 sin7/5pai*cos(-11/6pai)+tan(-15/4pai)*tan7/5pai
-
[sin^2(a+pai)cos(pai+a)cos(-a-2pai)]/[tan(pai+a)sin^3(pai/2+
-
[tan(pai-a)cos(2pai-a)sin(-a+3pai/2)]/[cos(-a-pai)sin(-pai-a