Find all the points of discontinuity of f defined by f(x)=|x|-|x+1|

Examine that sin |x| is a continuous function.

Show that the function defined by f(x) = |cos x| is a continuous function.

Show that the function defined by f(x)=cos(x^{2}) is a continuous function.

Find the values of a and b such that the function defined by

\( f(x)=\{5,if\;x \leq 2,ax+b,if\;2\)\( \)

\( \{21,if \;x\geq 10\)