Chứng minh
$dfrac{cos63^{\circ}cos3^{\circ} - cos87^{\circ}cos27^{\circ}}{cos132^{\circ}cos72^{\circ} - cos42^{\circ}cos18^{\circ}} = -tan24^{\circ}$
$tan830^{\circ} + tan770^{\circ} + tan740^{\circ} = tan470^{\circ}.tan410^{\circ}.tan380^{\circ}$
Loga
Sinh Học lớp 12
