Giải phương trình 3 . tan x - 3 = 0
1/ Giải phương trình sau:
\(tan^2\left(x+\dfrac{\pi}{3}\right)+\left(\sqrt{3}-1\right)tan\left(x+\dfrac{\pi}{3}\right)-\sqrt{3}=0\)
Đặt \(tan\left(x+\dfrac{\pi}{3}\right)=t\)
\(\Rightarrow t^2+\left(\sqrt{3}-1\right)t-\sqrt{3}=0\)
\(\Leftrightarrow t\left(t-1\right)+\sqrt{3}\left(t-1\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}t=1\\t=-\sqrt{3}\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}tan\left(x+\dfrac{\pi}{3}\right)=1\\tan\left(x+\dfrac{\pi}{3}\right)=-\sqrt{3}\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x+\dfrac{\pi}{3}=\dfrac{\pi}{4}+k\pi\\x+\dfrac{\pi}{3}=-\dfrac{\pi}{3}+k\pi\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=-\dfrac{\pi}{12}+k\pi\\x=-\dfrac{2\pi}{3}+k\pi\end{matrix}\right.\)
giải phương trình: \(\tan\left(\dfrac{3}{2}-x\right)+\dfrac{\sin x}{1+\cos x}=2\)
Phương trình tanx + tan(x + π 3 ) + tan(x + 2 π 3 ) = 3 3 tương đương với phương trình.
A. cot x = 3
B. cot 3x = 3
C. tan x = 3
D. tan 3x = 3
Giải phương trình sau :
\(2\tan^2x-3\tan x+2\cot^2x+3\cot x-3=0\)
Giải phương trình sau:
\(\tan\left(x+\dfrac{\pi}{3}\right)+\cot\left(\dfrac{\pi}{2}-3x\right)=0\)
Pt \(\Leftrightarrow\)\(tan\left(x+\dfrac{\pi}{3}\right)\)=\(-cot\left(\dfrac{\pi}{2}-3x\right)\)
\(\Leftrightarrow\)\(tan\left(x+\dfrac{\pi}{3}\right)\)=\(tan\left(\dfrac{\pi}{2}+\dfrac{\pi}{2}-3x\right)\)=\(tan\left(\pi-3x\right)\)
\(\Leftrightarrow\)\(x+\dfrac{\pi}{3}=\pi-3x+k\pi\)
\(\Leftrightarrow\)4\(x\)=\(\dfrac{4}{3}\pi+k\pi\)
\(\Leftrightarrow\) \(x=\) \(\dfrac{\pi}{3}+k\dfrac{\pi}{4}\)(\(k\in Z\))
\(pt\Leftrightarrow tan\left(x+\dfrac{\pi}{3}\right)=-cot\left(\dfrac{\pi}{2}-3x\right)\)
\(\Leftrightarrow tan\left(x+\dfrac{\pi}{3}\right)=cot\left(-\dfrac{\pi}{2}+3x\right)\)
\(\Leftrightarrow tan\left(x+\dfrac{\pi}{3}\right)=tan\left(\dfrac{\pi}{2}+\dfrac{\pi}{2}-3x\right)\)
\(\Leftrightarrow tan\left(x+\dfrac{\pi}{3}\right)=tan\left(\pi-3x\right)\)
\(\Leftrightarrow x+\dfrac{\pi}{3}=\pi-3x+k\pi\)
\(\Leftrightarrow4x=\dfrac{2\pi}{3}+k\pi\)
\(\Leftrightarrow x=\dfrac{\pi}{6}+\dfrac{k\pi}{4}\)
1) cho góc x thỏa mãn \(cosx=-\dfrac{4}{5}\) và \(\pi< x< \dfrac{3\pi}{2}\) tính \(P=tan\left(x-\dfrac{\pi}{4}\right)\)
2) giải phương trình \(2cosx-\sqrt{2}=0\)
3) phương trình lượng giác \(cos3x=cos\dfrac{\pi}{15}\) có nghiệm là
Giải các phương trình sau:
a) \(\sqrt 3 \tan 2x = - 1\); b) \(\tan 3x + \tan 5x = 0\)’
a) \(\sqrt 3 \tan 2x = - 1\;\; \Leftrightarrow \tan 2x = - \frac{1}{{\sqrt 3 }}\;\;\; \Leftrightarrow \tan 2x = \tan - \frac{\pi }{6}\; \Leftrightarrow 2x = - \frac{\pi }{6} + k\pi \)
\(\;\; \Leftrightarrow x = - \frac{\pi }{{12}} + \frac{{k\pi }}{2}\;\left( {k \in \mathbb{Z}} \right)\)
b) \(\tan 3x + \tan 5x = 0\;\; \Leftrightarrow \tan 3x = \tan \left( { - 5x} \right) \Leftrightarrow 3x = - 5x + k\pi \;\; \Leftrightarrow 8x = k\pi \;\; \Leftrightarrow x = \frac{{k\pi }}{8}\;\left( {k \in \mathbb{Z}} \right)\)
Giải phương trình sau:
a) $\tan ^2x+4\cos ^2x+7=4\tan x+8\cot x$
b) $6\sin ^2x+2\cos ^2x-2\sqrt{3}\sin 2x=14\sin \left(x-\frac{\pi }{6}\right)$
Giải phương trình
\(\dfrac{3}{cosx}+tan^2x=9\)
\(\dfrac{3}{cosx}+tan^2x=9\)
\(\Leftrightarrow\dfrac{sin^2x}{cos^2x}+\dfrac{3}{cosx}=9\)
\(\Leftrightarrow9cos^2x-3cosx-sin^2x=0\)
\(\Leftrightarrow9cos^2x-3cosx-1+cos^2x=0\)
\(\Leftrightarrow10cos^2x-3cosx-1=0\)
\(\Leftrightarrow\left(2cosx-1\right)\left(5cosx+1\right)=0\)
\(\Leftrightarrow cosx=\dfrac{1}{2}\)
\(\Leftrightarrow\left\{{}\begin{matrix}cosx=cos\dfrac{\pi}{3}\\cosx=-\dfrac{1}{5}\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=\pm\dfrac{\pi}{3}+k2\pi\\x=arcsin\left(-\dfrac{1}{5}\right)+k2\pi\end{matrix}\right.\)