Rút gọn pt lượng giác
1. A= 2sin(3\pi-2x)+3cos(2x+\frac{13\pi}{2})+5tan(x-3\pi)-2sin^{2}(\frac{9\pi}{4}-x)-cos(-2x)2.B=cot\frac{\pi}{18}.cot\frac{2\pi}{18}.cot\frac{3\pi}{18}...cot\frac{8\pi}{18}3. C=4cos15^{o}.cos21^{o}.cos24^{o}-cos12^{o}-cos18^{o}4. D=\frac{tan
^30{o}+tan40^{o}+tan50^{o}+tan60^{o}}{cos20^{o}}
Rút gọn pt lượng giác
1. A=
$2sin(3\pi-2x)+3cos(2x+\frac{13\pi}{2})+5tan(x-3\pi)-2sin^{2}(\frac{9\pi}{4}-x)-cos(-2x)
$2.B=
$cot\frac{\pi}{18}.cot\frac{2\pi}{18}.cot\frac{3\pi}{18}...cot\frac{8\pi}{18}
$3. C=
$4cos15^{o}.cos21^{o}.cos24^{o}-cos12^{o}-cos18^{o}
$4. D=
$\frac{tan30
^{o}+tan40^{o}+tan50^{o}+tan60^{o}}{cos20^{o}}
$