P/t \(\Leftrightarrow2cos2x.cosx-2.sin2x.cos2x=0\)
\(\Leftrightarrow cos2x\left(cosx-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}cos2x=0\\cosx=1\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}2x=\dfrac{\pi}{2}+k\pi\\x=2k\pi\end{matrix}\right.\) ( k \(\in Z\) )
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{\pi}{4}+\dfrac{k\pi}{2}\\x=2k\pi\end{matrix}\right.\)
cosx + cos2x + cos3x = 0
cosx + cos2x + cos3x + 1 = 0
\(cosx\sqrt{\frac{1}{cosx}-1}+cos3x\sqrt{\frac{1}{cos3x}-1}=1\)
sinx + sin2x + sin3x = 1 + cosx + cos2x
cos3x + sin3x + cosx - sinx = \(\sqrt{2}\)cos2x
sinx + sin2x + sin3x = cosx + cos2x + cos3x
Giúp mình với mn...
1)cos2x+cos22x+cos23x+cos24x=2
2) (1-tanx) (1+sin2x)=1+tanx
3) tan2x=sin3x.cosx
4) tanx +cot2x=2cot4x
5) sinx+sin2x+sin3x=cosx+cos2x+cos3x
6)sinx=√2 sin5x-cosx
7) 1/sin2x + 1/cos2x =2/sin4x
8) sinx+cosx=cos2x/1-sin2x
9)1+cos2x/cosx= sin2x/1-cos2x
10)sin3x+cos3x/2cosx-sinx=cos2x
\(cosx-2cos3x=1+\sqrt{3}sinx\)
\(sinx+sinx\left(x+\dfrac{\pi}{3}\right)+sin4x=sin\left(2x-\dfrac{\pi}{3}\right)\)
\(\left(1-\dfrac{1}{2sinx}\right)cos^22x=2sinx-3+\dfrac{1}{sinx}\)
( sinx -2cosx)cos2x + sinx = (cos4x - 1)cosx +\(\dfrac{cos2x}{2sinx}\)
\(\left(\dfrac{cos4x+sin2x}{cos3x+sin3x}\right)^2=2\sqrt{2}sin\left(x+\dfrac{\pi}{4}\right)+3\)
Sin4x - (sinx)^3.cosx+ 6.(sinx)^2.(cosx)^2 + 3.sinx.(cosx)^3 + 5cos4x=2
Giúp mk vs ạ cảm ơn....
Giải phương trình lượng giác bậc nhất đối với sinx và cosx:
\(cos3x-sinx=\sqrt{3}\left(cosx-sin3x\right)\)
giải pt sau :
\(\sqrt{3}sin4x-cos4x=sinx-\sqrt{3}cosx\)
1) giải pt:
a) cosx.cosx=cos2x.cos4x
b) cos5x.sin4x=cos3x.sin2x
c) sinx+sin2x=cosx+cos2x
d) sin2x+sin4x=sin6x
