1) giải pt:
a) cosx.cosx=cos2x.cos4x
b) cos5x.sin4x=cos3x.sin2x
c) sinx+sin2x=cosx+cos2x
d) sin2x+sin4x=sin6x
2sin²2x + sin6x - 1 = sin2x
sin2x + sin6x + 2sin²x - 1 = 0
1) Gia tri lon nhat cua ham so: y = sin6x + cos6x
\(cosx-2cos3x=1+\sqrt{3}sinx\)
\(sinx+sinx\left(x+\dfrac{\pi}{3}\right)+sin4x=sin\left(2x-\dfrac{\pi}{3}\right)\)
\(\left(1-\dfrac{1}{2sinx}\right)cos^22x=2sinx-3+\dfrac{1}{sinx}\)
( sinx -2cosx)cos2x + sinx = (cos4x - 1)cosx +\(\dfrac{cos2x}{2sinx}\)
\(\left(\dfrac{cos4x+sin2x}{cos3x+sin3x}\right)^2=2\sqrt{2}sin\left(x+\dfrac{\pi}{4}\right)+3\)
Giải các pt:
a) \(cos3x-sinx=\sqrt{3}\left(cosx-sin3x\right)\)
b) \(2cos^2x-3\sqrt{3}sin2x-4sin^2x=-4\)
c) \(\sqrt{3}\left(cos2x+sin3x\right)=sin2x+cos8x\)
d) \(cos2x-\sqrt{3}sin2x=\sqrt{3}sinx+cosx\)
e) \(sin8x-cos6x=\sqrt{3}\left(sin6x+cos8x\right)\)
Giải các phương trình sau :
a) \(\sin x+2\sin3x=-\sin5x\)
b) \(\cos5x\cos x=\cos4x\)
c) \(\sin x\sin2x\sin3x=\dfrac{1}{4}\sin4x\)
d) \(\sin^4x+\cos^4x=-\dfrac{1}{2}\cos^22x\)
sin6x + cos6x + 3sin2xcos2x
Giải PT:
\(\dfrac{1}{sinx}+\dfrac{1}{sin2x}+\dfrac{1}{sin4x}+\dfrac{1}{sin8x}=0\) trên khoảng \(\left(0;\dfrac{3\pi}{2}\right)\)
giải các phương trình sau: ( pt bậc nhất đối với sinx và cosx)
a, \(sinx+cosx=\sqrt{2}sin5x\)
b, \(\sqrt{3}sin2x+sin\left(\frac{\pi}{2}+2x\right)=1\)
c, \(\left(\sqrt{3}-1\right)sinx+\left(\sqrt{3}+1\right)cosx+\sqrt{3}-1=0\)
d, \(3sin^2x+\sqrt{3}sin2x=3\)
e, \(sin8x-cos6x=\sqrt{3}\left(sin6x+cos8x\right)\)
f,\(8cos2x=\frac{\sqrt{3}}{sinx}+\frac{1}{cosx}\)
g, \(cosx-\sqrt{3}sinx=2cos\left(\frac{\pi}{3}-x\right)\)
h, \(sin5x-cos5x=\sqrt{2}cos13x\)
i, \(\left(3cosx-4sinx+6\right)^2-9cosx+12sinx-16=0\)