\(cos2x+sin^2x+2cosx+1=0\)
\(\Leftrightarrow cos^2x-sin^2x+sin^2x+2cosx+1=0\)
\(\Leftrightarrow cos^2x+2cosx+1=0\)
\(\Leftrightarrow\left(cosx+1\right)^2=0\)
\(\Leftrightarrow cosx=-1\)
\(\Leftrightarrow x=\pi+k2\pi\left(k\in Z\right)\)
Vậy...
giải phương trình
1.\(sin^3x+2cosx-2+sin^2x=0\)
\(2.\frac{\sqrt{3}}{2}sin2x+\sqrt{2}cos^2x+\sqrt{6}cosx=0\)
3.\(2sin2x-cos2x=7sinx+2cosx-4\)
4.\(2cos2x-8cosx+7=\frac{1}{cosx}\)
5.\(cos^8x+sin^8x=2\left(cos^{10}x+sin^{10}x\right)+\frac{5}{4}cos2x\)
6.\(1+sinx+cos3x=cosx+sin2x+cos2x\)
7.\(1+sinx+cosx+sin2x+cos2x=0\)
Giải pt :
cos2x.sin4x + cos2x = 2cosx (sin x + cos x) -1
A, sin2 x- 4sinx +3=0
B, 2cos2x- cosx-1=0
C, 3sin2x- 2cosx +2=0
D, 3cosx+ cos2x -cos3x +1=2sinx.sin2x
E, tan2 x+(\(\sqrt{3}\) +1)tanx-\(\sqrt{3}\)=0
F, \(\dfrac{\sqrt{3}}{sin^2x}\)=3cotx + \(\sqrt{3}\)
A) 3Cos4x-Sin2x+Cos2x-2=0
B) 1/Sin2x+3Cotx+1=0
C) Cos2x-3Cosx=4Cos2x/2
Giair các phương trình sau :
15. \(\sqrt{3}\sin2x+\cos2x=2\cos x-1\)
26 .\(2\sin x^2+\sin7x-1=\sin x\)
7.\(\left(\sin2x+\cos2x\right)\cos x+2\cos2x-\sin x=0\)
sin\(^2\)x/2 - 2cosx +4 =0
Giải PT
a1) \(\dfrac{\left(1-2\sin x\right)\cos x}{\left(1+2\sin x\right)\left(1-\sin x\right)}=\sqrt{3}\)
a2) \(2\sin17x+\sqrt{3}\cos5x+\sin5x=0\)
a3) \(\)\(\cos7x-\sin5x=\sqrt{3}\left(\cos5x-\sin7x\right)\)
a4) \(\sqrt{3}\cos5x-2\sin3x\cos2x-\sin x=0\)
a5) \(\tan x+\cot x=2\left(\sin2x+\cos2x\right)\)
1) sin2x + 2cosx = 0
2) sin(2x -10*) = \(\dfrac{1}{2}\) (-120* <x< 90*)
3) cos(2x+10*)= \(\dfrac{\sqrt{2}}{2}\)(-180*<x<180*)
4) \(\sin^2\left(5x+\dfrac{2\pi}{5}\right)-\cos^2\)(\(\dfrac{x}{4}-\pi\)) =0
1) cos3x - cos4x + cos5x =0
2) sin3x + cos2x = 1 + 2sinx.cos2x
3) cos2x - cosx = 2 sin\(^2\)\(\dfrac{3x}{2}\)
4) cos\(^2\)2x + cos\(^2\)3x = sin\(^2\)x
5) sin3x.sin5x - cos4x.cos6x = 0
