\(L.H.S=\frac{cos({\pi}+x)cos(-x)}{sin({\pi}-x)cos(\frac{\pi}{2}+x)}\)
\(=\frac{[-cos\,x][cos\,x]}{(sin\,x)(-sin\,x)}\)
\(\frac{-cos^2x}{-sin^2x}\)
\(=cot^2x\)
\(=R.H.S.\)
\(f(x) = \begin{cases} x^2, & \quad 0≤x≤3\\ 3x, & \quad 3≤x≤10 \end{cases}\)
The relation g is defined by
\(g(x) = \begin{cases} x^2, & \quad 0≤x≤2\\ 3x, & \quad 2≤x≤10 \end{cases}\)
Show that f is a function and g is not a function.