`~rai~`
\(A=\cos^274^\circ+\tan67^\circ-\dfrac{\cot37^\circ}{\tan53^\circ}-\cot23^\circ+\cos^216^\circ\\\quad=\cos^274^\circ+\tan67^\circ-\dfrac{\cot37^\circ}{\cot37^\circ}-\tan67^\circ+\sin^274^\circ\\\quad=(\cos^274^\circ+\sin^274^\circ)+(\tan67^\circ-\tan67^\circ)-\dfrac{\cot37^\circ}{\cot37^\circ}\\\quad=1+0-1=0.\\\text{Công thức áp dụng:}\\+)\sin\alpha=\cos\alpha(90^\circ-\alpha)\\+)\cos\alpha=\sin(90^\circ-\alpha)\\+)\tan\alpha=\cot(90^\circ-\alpha)\\+)\cot\alpha=\tan(90^\circ-\alpha)\\+)\sin^2\alpha+\cos^2\alpha=1.\)
