In a $dc$ motor,induced $e.m.f.$ will be maximum

Which of the following statements is false?

$A$ transverse harmonic wave on a string is described by $y = 3 \sin(36t + 0.018x + \frac{\pi}{4})$,where $x$ and $y$ are in $cm$ and $t$ is in $s$. The least distance between two successive crests in the wave is .... $m$. (in $.5$)

If $f(0)=0, f(1)=1, f(2)=2$ and $f(x)=f(x-2)+f(x-3)$ for $x=3, 4, 5, \ldots$, then $f(9)$ is equal to

If $y = \log_{\cos x} \sin x$,then $\frac{dy}{dx}$ is equal to

Heating an aqueous solution of aluminium chloride to dryness will give: