Simplify the composite function $a\(\left\)(b\(\left\)(c\(\left\)(x\(\right\))\(\right\))\(\right\))$ given the following:
$a\(\left\)(x\(\right\))=-x^3$
$b\(\left\)(x\(\right\))=\(\cos\]\left\)(x\(\right\))$$c\(\left\)(x\(\right\))=\(\sqrt{x}\)$