高中物理學到的三角函數?

2016-07-06 10:38 am
請問tan280°為何=-tan80°呢
還有sin(90-X)cos(360+X)+sin(-X)cos(270-X)=? 需要算法~~

回答 (1)

2016-07-06 11:06 am
✔ 最佳答案
1 Tan280°為何=-Tan80°呢
Sol
Tan280°
=Tan(360°-80°)
=-Tan80°
2 Sin(90°-x)Cos(360°+x)+Sin(-x)Cos(270°-x)=?
Sol
Sin(90°-x)=Cosx
Cos(360°+x)=Cosx
Sin(-x)=-Sinx
Cos(270°-x)=-Sinx
Sin(90°-x)Cos(360°+x)+Sin(-x)Cos(270°-x)
=CosxCosx+(-Sinx)(-Sinx)
=Cos^2 x+Sin^2 x
=1


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