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 ...
\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)....
If cos alpha+cos beta=a sin alpha+sin beta=balpha-beta=2 theta then (c... 04:23 If cos a+cos beta=a,sin a+sin beta=b are alpha-beta=2 theta, then (cos... 03:11 If (cos3 alpha)/(cos alpha)=(1)/(3),0<alpha<(pi)/(2) then (sin3 alpha)... 03:18 If cosalpha+...
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
\$\sin 2 \alpha \cos \alpha = 2 \sin \alpha \left( 1 - \sin ^ { 2 } \alpha \right)\$ 证明:. 相关知识点: 试题来源: 解析 证明: 证明: \$\sin 2 \alpha \cos \alpha = 2 \sin \alpha \cos \alpha \cos \alpha\$ \$= 2 \sin \alpha \cdot \cos ^ { 2 } \...
【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...
(sin(α)+cos(α))2 Quiz Trigonometry (sinα+cosα)2 Similar Problems from Web Search If sinα+cosα=1.2, then what is sin3α+cos3α? https://math.stackexchange.com/questions/2001078/if-sin-alpha-cos-alpha-1-2-then-what-is-sin3-alpha-cos3-alpha Hint :(sina+cosa)(sin2a−sina...
sin^2α +cos^2α =1的变形公式:$sin^2\alpha =1-cos^2\alpha =(1+cos\alpha )(1-cos\alpha )⟹ (si
解: \alpha 是第二象限的角,所以\cos\alpha ∴ \cos\alpha =-\root \of {1-{\sin\alpha }^2}=-\root \of {1-(\frac{4}{5}) ^2}=-\frac{3}{5},∴ \sin2\alpha =2\sin\alpha \cos\alpha =2\times \frac{4}{5} \times (-\frac{3}{5} )=-\frac{24}{25},\cos2\a...
若\(\alpha\)是第一象限角,则\(\sin 2 \alpha\),\(\cos \dfrac{ \alpha }{2}\),\(\tan\dfrac{ \alpha }{2}\)中一定为正值的个数为___. 相关知识点: 试题来源: 解析 \(2\) 由\(\alpha\)是第一象限角,得\(2k \pi < \alpha < \dfrac{ \pi }{2}+2k \pi\),\(k...