Question

5cos (1-3x)+2=0

Answer 1

\(5cos\left(1-3x\right)=-2\)

\(cos\left(1-3x\right)=-\dfrac{2}{5}\)

\(1-3x=cos^{-1}\left(-\dfrac{2}{5}\right),2\pi-cos^{-1}\left(-\dfrac{2}{5}\right)\)

\(1-3x=2\pi n+cos^{-1}\left(-\dfrac{2}{5}\right),n\in Z\)​\(1-3x=2\pi n+2\pi-cos^{-1}\left(-\dfrac{2}{5}\right),n\in Z\)\(x=\dfrac{2\pi n+cos^{-1}\left(-\dfrac{2}{5}\right)-1}{3},n\in Z\)\(x=\dfrac{2\pi n+2\pi-cos^{-1}\left(-\dfrac{2}{5}\right)-1}{3},n\in Z\)

sai thì thông cảm ạ