The slope of the tangent to the curve $y = ln\, (cos\,x)$ a $x = \frac{3\pi}{4}$ is
$1$
$-1$
$\ln \,\sqrt 2 $
$\frac{1}{{\sqrt 2 }}$
The greatest value of the function $-5 \sin \theta+12 \cos \theta$ is
If $log_{10} (xy) = 2$, then the value of $xy$ is