\(\Leftrightarrow\left\{{}\begin{matrix}2\left(2cos^2x-1\right)-4cosx-1=0\\sinx\ge0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}4cos^2x-4cosx-3=0\\sinx\ge0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}\left[{}\begin{matrix}cosx=\frac{3}{2}\left(l\right)\\cosx=-\frac{1}{2}\end{matrix}\right.\\sinx\ge0\end{matrix}\right.\)
\(\Leftrightarrow x=\frac{2\pi}{3}+k2\pi\)
tìm x biết \(\left\{{}\begin{matrix}2sin2x-4cosx=1\\sinx\ge0\end{matrix}\right.\)
giải pt : 1, \(\dfrac{\left(1-cosx\right)^2+\left(1+sinx\right)^2}{4\left(1-sinx\right)}-tan^2sinx=\dfrac{1}{2}\left(1+sinx\right)+tan^2x\)
Giải pt
\(a.sin^3x+cos^3x=\dfrac{\sqrt{2}}{2}\)
\(b.sin^3x+cos^3x-sinx-cosx=cos2x\)
\(c.\left(2+\sqrt{2}\right)\left|sinx+cosx\right|-sin2x=1+2\sqrt{2}\)
giải pt
a) \(cosx\left(3tanx-\sqrt{3}\right)=0\)
b) \(\frac{\left(2-sinx\right)\left(\sqrt{3}cosx-1\right)}{1+sinx}+2=sinx\)
c) \(\frac{tanx-sinx}{sin^3x}=\frac{1}{cosx}\)
d) \(\frac{sin3x.cosx-sinx.cos3x}{cos^2x}=2\sqrt{3}\)
HELPING NOW!!!
Giair phương trình lượng giác sau:
1) cosx - cos2x +cos3x = 0
2) cos2x - sin2x = sin3x + cos4x
3) cos2x + 2sinx - 1 - 2sinxsosx = 0
4) 1+ sinx - cosx = sin2x - cos2x
5) \(\sqrt{2}\) sin (2x+\(\dfrac{\pi}{4}\)) - sinx - 3cosx +2 =0
6) sin2x + 2cos2x = 1+sinx - 4cosx
giải các pt
a) \(4cos^2\left(6x-2\right)+16cos^2\left(1-3x\right)=13\)
b) \(cos\left(2x+150^o\right)+3sin\left(15^o-x\right)-1=0\)
c) \(\sqrt{3}sin2x+\sqrt{3}sinx+cos2x-cosx=2\)
d) \(cos2x-\sqrt{3}sin2x-\sqrt{3}sinx+4=cosx\)
Giải
a) \(cos\left(\pi sinx\right)=cos\left(3\pi sinx\right)\)
b) \(tan\left[\frac{\pi}{4}\left(sinx+1\right)\right]=1\)
giải các pt
a) \(cos^2\left(\frac{\pi}{3}+x\right)+4cos\left(\frac{\pi}{6}-x\right)=4\)
b) \(5cos\left(2x+\frac{\pi}{3}\right)=4sin\left(\frac{5\pi}{6}-x\right)-9\)
c) \(2sin^2x+\sqrt{3}sin2x+2\sqrt{3}sinx+2cosx=2\)
d) \(2sin^2x+\sqrt{3}sin2x+4=4\left(\sqrt{3}sinx+cosx\right)\)
Giải pt (2cos2x-1)(sin2x+cos2x)=1
