Question

1.Sin²2x-cos2x+1=0

2.sin²x/4-3cosx/4=0

3.tan7x-3cot7x+2=0

Answer 1

1.

\(1-cos^22x-cos2x+1=0\)

\(\Leftrightarrow-cos^22x-cos2x+2=0\)

\(\Leftrightarrow\left[{}\begin{matrix}cos2x=1\\cos2x=-2\left(l\right)\end{matrix}\right.\)

\(\Leftrightarrow x=k\pi\)

2.

Bạn ghi lại đề, ko hiểu

3.

ĐKXĐ:...

\(tan7x-\frac{3}{tan7x}+2=0\)

\(\Leftrightarrow tan^27x+2tan7x-3=0\)

\(\Rightarrow\left[{}\begin{matrix}tan7x=1\\tan7x=-3\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\frac{\pi}{28}+\frac{k\pi}{7}\\x=\frac{1}{7}arctan\left(-3\right)+\frac{k\pi}{7}\end{matrix}\right.\)