Bài 3:
$a)\quad A =\dfrac{\sin58^\circ}{\cos32^\circ}=\dfrac{\cos32^\circ}{\cos32^\circ}= 1$
$\qquad B = \cot18^\circ - \tan72^\circ = \tan72^\circ - \tan72^\circ = 0$
$b)$
Ta có:
$\cot40^\circ = \tan50^\circ$
$\cot14^\circ = \tan76^\circ$
Do: $\tan17^\circ < \tan25^\circ < \tan50^\circ < \tan76^\circ$
nên $\tan17^\circ < \tan25^\circ < \cot40^\circ < \cot14^\circ$
Bài 4:
Ta có:
$\cot N =\dfrac{NQ}{MQ}$
$\cot P =\dfrac{PQ}{MQ}$
mà $NQ = 3 < 6 = PQ$
nên $\dfrac{NQ}{MQ} < \dfrac{PQ}{MQ}$
hay $\cot N < \cot P$
