mshd.net
当前位置:首页 >> Cos75°Cos15°%sin75°sin15°=????? >>

Cos75°Cos15°%sin75°sin15°=?????

见图

和差化积公式: sin15°+sin75° =2sin[(15°+75°)/2]cos[(15°-75°)/2] =2sin45°cos(-30°) =2sin45°cos30° =2×(√2/2)×(√3/2) =√6/2 或者sin15°+sin75° =sin(45°-30°)+sin(45°+30°) =(sin45°cos30°-sin30°cos45°)+(sin45°cos30°+sin30°cos45°...

如图

0.5

sin75°=sin(45°+30°)=sin45°cos30°+cos45°sin30°=(√6+√2)/4 cos75=cos(30+45)=cos30cos45-sin30sin45=√6/4-√2/4=(√6-√2)/4

sin75°sin135°+sin15°cos45° =cos15°sin45°+sin15°cos45° =sin(45°+15°) =sin60° =√3/2

cos75-cos15=cos(45+30)-cos(45-30)=cos45cos30-sin45sin30-(cos45cos30+sin45sin30) =cos45cos30-sin45sin30-cos45cos30-sin45sin30=-2sin45sin30=-2*(√2)/2*1/2=-(√2)/2

原式=【sin(75°+10°)-cos75°sin10°】/【cos(75°-10°)-sin75°sin10°】 =(sin75°cos10°+cos75°sin10°-cos75°sin10°)/(cos75°cos10°+sin75°sin10°-sin75°sin10°) =(sin75°cos10°)/(cos75°cos10°) =tan75° =tan(45°+30°) =(tan45°+tan30°)/(1-tan45°...

cos75°+cos165°=cos75-cos15=cos75+sin75=cos(45+30)+sin(45+30)=cos45cos30-sin45sin30+sin45cos30+cos45+sin30=根号6/2

sin15cos75+cos15sin105=sin15sin15+cos15cos15=1

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