nnxh.net
当前位置:首页 >> sin20sin40sin80 >>

sin20sin40sin80

=-sin20(cos120-cos40)/2 =sin20/4+sin20cos40/2 =sin20/4+(sin60-sin20)/4 =sin60/4 =八分之根号下三

解:这是和差化积公式,如果记不住可以采用如下法解决。sin20+sin40=sin(30-10)+sin(30+10)=sin30cos10-cos30sin10+sin30cos10+cos30sin10=2sin30cos10.sin80+sin40=sin(60+20)+sin(60-20)=sin60cos20+cos60sin20+sin60cos20-cos60sin20=2sin60c...

由积化和差公式: sin20°sin40°sin80° =-1/2(cos60-cos(-20))sin80 =-1/4sin80+1/2cos20*sin80 =-1/4sin80+1/2*1/2(sin100+sin60) =-1/4sin80+1/4sin100+1/4*(根号3/2) =(根号3/8)

肯定对 sin20sin40sin80 =-1/2(cos60-cos20)sin80 =-1/4*sin80+1/2*cos20*sin80 =-1/4*sin80+1/2*[1/2*(sin60+sin100)] =-1/4*sin80+1/4*sin60+1/4*sin100 =1/4*sin60 =1/4*[(根号3)/2] =(根号3)/8 tan20tan40tan80=tan20tan(60-20)tan(60+20) =...

解:这是和差化积公式,如果记不住可以采用如下法解决。sin20+sin40=sin(30-10)+sin(30+10)=sin30cos10-cos30sin10+sin30cos10+cos30sin10=2sin30cos10sin80+sin40=sin(60+20)+sin(60-20)=sin60cos20+cos60sin20+sin60cos20-cos60sin20=2sin60cs...

由积化和差公式: sin20°sin40°sin80° =-1/2(cos60-cos(-20))sin80 =-1/4sin80+1/2cos20*sin80 =-1/4sin80+1/2*1/2(sin100+sin60) =-1/4sin80+1/4sin100+1/4*(根号3/2) =(根号3/8)

sin(20°) = 0.34202014332567 sin(80°) = 0.98480775301221 sin(40°) = 0.64278760968654 所以这个式子的值就是:0.975042

用sinθsin(60-θ)sin(60+θ)=1/4sin3θ公式 θ=20 答:结果=3/16

观察到自变量间是2倍的关系 考虑用二倍角公式 解:原式=(2cos10 sin10 sin 20 sin40)/(2cos 10) =(2cos20 sin20 sin40)/(4cos10) =(2cos40 sin 40)/(8cos 10) =cos80 / 8cos 10 ∵cos80=-cos 10 ∴原式=- 1/8 希望对您有帮助

sin20sin40sin80*(sin60) =-1/2(cos60-cos20)sin80*(根号3/2) =-1/4*sin80+1/2*cos20*sin80*根号3/2 =-1/4*sin80+1/2*[1/2*(sin60+sin100)]*根号3/2 =(-1/4*sin80+1/4*sin60+1/4*sin100)*根号3/2 =1/4*(sin60)^2 =1/4*根号3/2*根号3/2 =3/16

网站首页 | 网站地图
All rights reserved Powered by www.nnxh.net
copyright ©right 2010-2021。
内容来自网络,如有侵犯请联系客服。zhit325@qq.com