Question

Вычислить 4sin^2 120°-2cos 60°+ корень 27 tg 660°

Answer 1

$4\sin^2120^\circ-2\cos 60^\circ+ \sqrt{27} \mathrm{tg} 660^\circ=$

$=4\sin^2(180^\circ-60^\circ)-2\cos 60^\circ+ \sqrt{27} \mathrm{tg} (660^\circ-4\cdot180^\circ)=$

$=4\sin^2 60^\circ-2\cos 60^\circ+ \sqrt{27} \mathrm{tg} (-60^\circ)=$

$=4\sin^2 60^\circ-2\cos 60^\circ- 3\sqrt{3} \mathrm{tg} 60^\circ=$

$=4\cdot\left(\dfrac{\sqrt{3} }{2}\right)^2-2\cdot\dfrac{1}{2} - 3\sqrt{3} \cdot\sqrt{3} =4\cdot\dfrac{3}{4} -1 - 9=3-10=-7$