[tex]\dfrac{x}{2}+\dfrac{3\pi}{4}=t\Rightarrow \dfrac{x}{2}=t-\dfrac{3\pi}{4}[/tex]
[tex]\Rightarrow \dfrac{3x}{2}+\dfrac{\pi}{4}=3\left ( t-\dfrac{3\pi}{4} \right )+\dfrac{\pi}{4}=3t-2\pi[/tex]
Phương trình trở thành:
[tex]sin(3t-2\pi)=2sin^3t\Leftrightarrow sin3t=2sin^3t\Leftrightarrow 3sint-4sin^3t=2sin^3t\Leftrightarrow ez...[/tex]