3. Find all extrema of the function $y=\sin ^{2} 3 x$ on the interval $(0 ; 0.6)$.
Solution: $y=\sin ^{2} 3 x,(0 ; 0.6) ; y^{\prime}=2 \sin 3 x \cdot \cos 3 x=\sin 6 x=0 ; x=\frac{\pi k}{6}$ $x=0, y_{\max }\left(\frac{\pi}{6}\right)=1$

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