\(L.H.S=\frac{cos({\pi}+x)cos(-x)}{sin({\pi}-x)cos(\frac{\pi}{2}+x)}\)
\(=\frac{[-cos\,x][cos\,x]}{(sin\,x)(-sin\,x)}\)
\(\frac{-cos^2x}{-sin^2x}\)
\(=cot^2x\)
\(=R.H.S.\)

Prove that. \(sin^2 \frac{π}{6}+cos^2 \frac{π}{3}–tan^2 \frac{π}{4}=-\frac{1}{2}\)
Find the mean deviation about the mean for the data 38, 70, 48, 40, 42, 55, 63, 46, 54, 44.