高一数学题 哥哥姐姐帮偶个忙

来源：百度知道 编辑：UC知道 时间：2024/06/01 21:49:14
tan（70`）×cos(10`)*(1-√3*tan(20`))

sin(x);sin(0.5x)=8;5 求cos(x) cot0.5X

过程 一定要对啊
写得好加分噢~~~~

tan（70`）×cos(10`)*(1-√3*tan(20`))=(sin70/cos70)×cos10×2(1/2-√3/2×(sin20/cos20))
=(sin70/cos70)×cos10×2(1/2-√3/2×(cos70/sin70))
=cos10×sin70/cos70×2/sin70(cos60sin70-sin60cos70)
=2cos10/cos70×sin(70-60)
=2cos10sin10/sin20
=1

sin(x);sin(0.5x)=8;5 求cos(x) cot0.5Xsin(x);sin(0.5x)
=2sin(0.5x)cos(0.5x)/sin(0.5x)
=2cos(0.5x)
=8/5
求得cos(0.5x)=4/5 sin(0.5x)=3/5
cos(x) cot0.5X
=[cos2(0.5x)-sin2(0.5x)]cos(0.5x)/sin(0.5x)
把cos(0.5x)=4/5 sin(0.5x)=3/5代入上试求得
cos(x) cot0.5X=7/15