\(sin^2\dfrac{x}{2}-2cosx+4=0\)
\(\Leftrightarrow-\dfrac{1}{2}cosx-2cosx+\dfrac{9}{2}=0\)
\(\Leftrightarrow\dfrac{5}{2}cosx=\dfrac{9}{2}\)
\(\Leftrightarrow cosx=\dfrac{9}{5}\)
\(\Rightarrow\) phương trình vô nghiệm.
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
cos2x+sin\(^2\)x+2cosx+1=0
\(\frac{cos^2X-2cos\left(X+\frac{3Π}{4}\right)Sin\left(3x-\frac{Π}{4}\right)-2}{2cosx-\sqrt{2}}=0\)
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.\(1+sinx+cosx+sin2x+cos2x=0\)
Câu 1)
a) 2cos2x-3cosx+1=0
b)2sin2x+√2 sin4x=0
C)sin2x/2-2cosx/2+2=0
d)tanx-2cotx+1=0
Giải pt :
cos2x.sin4x + cos2x = 2cosx (sin x + cos x) -1
GTLN của hàm số y = sin2x + 2cosx +2
Tìm GTLN và GTNN của hàm số : 1. y = sinx + 2cosx +1 / 2sinx + cosx + 3
2.y= 2sin^2sinx - 3 sinx cosx + cos^2 x
Giải phương trình : 1. 2sin^2 * 2x + sin7x -1 = sinx
2.cos 4x + 12 sin^2 x -1 = 0
\(\dfrac{2sin^3x+2\sqrt{3}sin^2x.cosx-2sin^2x+cos\left(2x+\dfrac{\pi}{3}\right)}{2cosx-\sqrt{3}}=0\)
