【解析】 $$ \cos 2 \alpha + \cos 2 \beta = 2 \cos ( \alpha + \beta ) \cos ( \alpha - \beta ) $$ 证明: $$左边 \\ = \cos \left[ ( \alpha + \beta ) + ( \alpha - \beta ) \right] \cos \left[ ( \alpha + \beta ) - ( \alpha - \beta ) \right] \\ = ...
【题目】若$$ \cos ( \alpha - \beta ) = \frac { \sqrt { 5 } } { 5 } , \cos 2 \alpha = \frac { \sqrt { 1 0 } } { 1 0 } $$,并且α、β均为锐角,且$$ \alpha 相关知识点: 试题来源: 解析 【解析】答案:C. 因为$$ 0 ...
If cos(alpha+beta)=(5)/(13) and cos(alpha-beta)=(4)/(5) then find the value of tan2 beta If cos alpha=(4)/(5) and cos beta=(5)/(13), prove that (cos(alpha-beta))/(2)=(8)/(sqrt(65)) If cos alpha=(3)/(5) and cos beta=(5)/(13), then cos^(2)backslash(alph...
$$ (3)正切公式的变形:$$ \tan \alpha \pm \tan \beta = \tan ( \alpha \pm \beta ) ( 1 + \tan \alpha \tan \beta ) . $$ 2.常见的配角技巧 $$ 2 \alpha = ( \alpha + \beta ) + ( \alpha - \beta ) , \alpha = ( \alpha + \beta ) - \beta , \beta = \fra...
beta = - \frac { 5 } { 1 3 } , \beta \in ( \pi , \frac { 3 \pi } { 2 } $$ ∴$$ . \cos \beta = - \sqrt { 1 - \sin ^ { 2 } \beta } = - \frac { 1 2 } { 1 3 } $$ $$∴ . \cos ( \alpha + \beta ) = \cos \alpha \cos \beta - \...
\alpha = \_ , \sin ^ { 2 } \alpha = \_ \_ \_ $$___.(2)二倍角的升幂公式:$$ 1 + \cos 2 \alpha = \_ , 1 - \cos 2 \alpha $$=___.(3)T$$ ( \alpha \pm \beta ) $$的公式变形;$$ \tan \alpha \pm \tan \beta = \_ ; $$$ \tan \alpha \tan \beta ...
$$$ \tan 2 \alpha = \frac { 2 \tan \alpha } { 1 - \tan ^ { 2 } \alpha } . $$ 相关知识点: 试题来源: 解析 注解2 二倍角公式实际就是由两角和公式中令$$ \beta = \alpha $$所得. 逆用即为“降幂公式”,在考题中常有体现. 反馈 收藏 ...
点2 (1) $$ \frac { 1 + \cos 2 \alpha } { 2 } $$ $$ \frac { 1 - \cos 2 \alpha } { 2 } $$ (2)2$$ 2 \cos ^ { 2 } a $$ 2.$$ \sin ^ { 2 } $$a (3)t(3)tan(α±β)(1千tan atanβ)$$ \frac { \tan \alpha - \tan \beta } { \tan...
点2(1) $$ \frac { 1 + \cos 2 \alpha } { 2 } $$ $$ \frac { 1 - \cos 2 \alpha } { 2 } $$ (2)2$$ 2 \cos ^ { 2 } a $$a 2$$ \sin ^ { 2 } $$a (3)t(3)tan(α±β)(1+tanatanβ)$$ \frac { \tan \alpha - \tan \beta } { \tan ( ...
$$ \cos ^ { 2 } \alpha = \_ , \sin ^ { 2 } \alpha = \_ \_ \_ $$___.(2)二倍角的升幂公式:$$ 1 + \cos 2 \alpha = \_ , 1 - \cos 2 \alpha $$=___.(3)T(a±β)的公式变形;$$ \tan \alpha \pm \tan \beta = \_ ; $$$ \tan \alpha \tan \beta ...