Possible Duplicate:
$\arcsin$ written as $\sin^{-1}(x)$
When I learnt the trig identity $\sin^2\theta + \cos^2\theta \equiv 1$, I learnt that $\sin^2\theta = (\sin\theta)^2$.
So why isn't $\sin^{-1}\theta = (\sin\theta)^{-1} = \dfrac{1}{\sin\theta}$?
Because $\csc\theta = \dfrac{1}{\sin\theta} $, but $\csc\theta \ne \sin^{-1}\theta$
How can these two same notations, just with different numbers, mean different things?