Practicing Success
The maximum value of the function sin x (1 + cos x) is |
3 $\frac{3\sqrt{3}}{4}$ 4 $3\sqrt{3}$ |
$\frac{3\sqrt{3}}{4}$ |
$y=\sin x(1+\cos x)=\sin x+\frac{1}{2} \sin 2 x$ $\Rightarrow \frac{d y}{d x}=\cos x+\cos 2 x=0$ ∴ $\frac{d y}{d x}=0 \Rightarrow \cos 2 x=-\cos x=\cos (\pi-x)$ $\Rightarrow 2 x=\pi-x \Rightarrow x=\frac{\pi}{3}$ $\frac{d^2 y}{d x^2}=-\sin x-2 \sin 2 x<0$ for $x=\frac{\pi}{3}$ ∴ y is maximum at $x=\frac{\pi}{3}$ and its value is $\frac{3 \sqrt{3}}{4}$. |