容儿农重府斗应量满将何学员往6.4命题\sin ^2\alpha \cos ^2\alpha =1恒成立'的否定是(容儿农重府斗应量满将何学员往容儿农重府斗应量满将何学员
\cos 2\alpha =\cos^2\alpha -\sin^2\alpha ,\tan 2\alpha =\frac{2\tan \alpha }{1-\tan^2\alpha },同理,我们可以证得如下三倍角公式:\sin 3\alpha =3\sin\alpha -4\sin^3\alpha ,\cos 3\alpha =___(要求用\cos\alpha 来表示),\tan 3\alpha =___(要求用\tan\alpha 来表示)....
sin^2α +cos^2α =1的变形公式:$sin^2\alpha =1-cos^2\alpha =(1+cos\alpha )(1-cos\alpha )⟹ (si
试题来源: 解析 1设直角△ABC中,∠C =90°, ∠A=α ,a的 对边是a,邻边是b,斜边是c. 则有 a^2+b^2=c^2 , sinα=a/c , cosα=b/c , 所以 sin^2α+cos^2α=(a^2+b^2)/(c^2)=(c^2)/(c^2)=1 故答案为1. 反馈 收藏 ...
百度试题 结果1 题目同角三角函数的基本关系为:,,利用同角三角函数的基本关系求解下题:已知,___. 相关知识点: 试题来源: 解析 ∵,,∴,∵,∴原式, 首先根据条件 可得 ,再根据 可得 ,然后再代入 即可. 反馈 收藏
(1)降幂公式:sin^2\alpha =___,cos^2\alpha =___;(2)升幂公式:1+cos\alpha =___,1-cos\alpha
由\sin \alpha =2\cos \alpha ,得\tan \alpha =2, 所以;\sin \alpha \cos \alpha =\frac{1}{2}\sin 2\alpha =\frac{1}{2}\times \frac{2\tan \alpha }{1+{{\tan }^{2}}\alpha }=\frac{1}{2}\times \frac{2\times 2}{1+4}=\frac{2}{5}. 故答案为:\frac{2}{5}.反馈...
【解析】\because \left\{\begin{array}{l}\sin \alpha -2\cos \alpha =1\\ {\sin }^{2}\alpha +{\cos }^{2}\alpha =1\end{array}\right.\Rightarrow \left\{\begin{array}{l}\cos \alpha =-\dfrac{4}{5}\\ \sin \alpha =-\dfrac{3}{5}\end{array}\right.或\left\{\begi...
Why is cosαsinβ=21[sin(α+β)−sin(α−β)]? https://www.quora.com/Why-is-cos-alpha-sin-beta-frac-1-2-sin-alpha+-beta-sin-alpha-beta To show why, our goal will be to manipulate the right si...
所以;0<{}\alpha +\beta < {} \pi ,又\cos \left( \alpha +\beta \right)=\frac{1}{7}, 所以;\sin \left( \alpha +\beta \right)=\frac{4\sqrt{3}}{7}, 则\cos \beta =\cos \left[ \left( \alpha +\beta \right)-\alpha \right] ~~~=\cos \left( \alpha +\beta \right)...