Đáp án:
$\begin{array}{l}
A = \sin {10^0} + \sin {40^0} - \cos {55^0} - \cos {80^0}\\
= \left( {\sin {{10}^0} - \cos {{80}^0}} \right) + 0,642 - 0,573\\
= 0 + 0,07\\
= 0,07\\
B = \cos {15^0} + \cos {35^0} - \sin {55^0} - \sin {75^0}\\
= \left( {\cos {{15}^0} - \sin {{75}^0}} \right) + \left( {\cos {{35}^0} - \sin {{55}^0}} \right)\\
= \left( {\cos {{15}^0} - \cos {{15}^0}} \right) + \left( {\cos {{35}^0} - \cos {{35}^0}} \right)\\
= 0\\
C = \dfrac{{\tan {{27}^0}.\tan {{63}^0}}}{{\cot {{63}^0}.\cot {{27}^0}}} = \dfrac{{\tan {{27}^0}.\tan {{63}^0}}}{{\tan {{27}^0}.tan{{63}^0}}} = 1\\
D = \dfrac{{\cot {{20}^0}.\cot {{45}^0}.\cot {{70}^0}}}{{\tan {{20}^0}.\tan {{45}^0}.\tan {{70}^0}}} = 1
\end{array}$
