Giúp mình với mình ảm anh trc

17
$T = \dfrac{8}{3}\sin^2 60^{\circ} \cdot \cos 30^{\circ} - \tan 60^{\circ} + 10 \cdot \cot 45^{\circ}$
$T = \dfrac{8}{3} \cdot \left(\dfrac{\sqrt{3}}{2}\right)^2 \cdot \dfrac{\sqrt{3}}{2} - \sqrt{3} + 10 \cdot 1$
$T = \dfrac{8}{3} \cdot \dfrac{3}{4} \cdot \dfrac{\sqrt{3}}{2} - \sqrt{3} + 10$
$T = \dfrac{2 \cdot \sqrt{3}}{2} - \sqrt{3} + 10$
$T = \sqrt{3} - \sqrt{3} + 10$
$T = 0 + 10$
$T = 10$
18
$F = \sin 59^{\circ} - \cos 59^{\circ} + \sin 31^{\circ} - \cos 31^{\circ}$
Ta có: $\cos 59^{\circ} = \sin (90^{\circ} - 59^{\circ}) = \sin 31^{\circ}$
$\sin 59^{\circ} = \cos (90^{\circ} - 59^{\circ}) = \cos 31^{\circ}$
$F = \cos 31^{\circ} - \sin 31^{\circ} + \sin 31^{\circ} - \cos 31^{\circ}$
$F = (\cos 31^{\circ} - \cos 31^{\circ}) + (-\sin 31^{\circ} + \sin 31^{\circ})$
$F = 0 + 0$
$F = 0$
19
$A = \dfrac{\sin 39^{\circ}}{\cos 51^{\circ}} - \tan 20^{\circ} \cdot \tan 70^{\circ}$
Ta có: $\cos 51^{\circ} = \sin (90^{\circ} - 51^{\circ}) = \sin 39^{\circ}$
$\tan 70^{\circ} = \cot (90^{\circ} - 70^{\circ}) = \cot 20^{\circ}$
$A = \dfrac{\sin 39^{\circ}}{\sin 39^{\circ}} - \tan 20^{\circ} \cdot \cot 20^{\circ}$
$A = 1 - 1$
$A = 0$
20,
$B = 6\sin 30^{\circ} - 4(\sin^2 60^{\circ} - \cos 60^{\circ}) + \tan^2 45^{\circ}$
$B = 6 \cdot \dfrac{1}{2} - 4\left(\left(\dfrac{\sqrt{3}}{2}\right)^2 - \dfrac{1}{2}\right) + 1^2$
$B = 3 - 4\left(\dfrac{3}{4} - \dfrac{1}{2}\right) + 1$
$B = 3 - 4\left(\dfrac{3}{4} - \dfrac{2}{4}\right) + 1$
$B = 3 - 4\left(\dfrac{1}{4}\right) + 1$
$B = 3 - 1 + 1$
$B = 3$