You use sin when you have the angle and you are looking for a side (or a ratio)
You use inverse sin (sometimes called arc sin) when you have the sides or the ratio and you are finding the angle!
So sine to find a side and inverse sin to find the angle.
sin(angle)=opphypsin−1(opphyp)=angle
sinh is a compicated thing that you probably wont use unless you study maths at a high level.
but if you are interested you can look here http://en.wikipedia.org/wiki/Hyperbolic_function
You use sin when you have the angle and you are looking for a side (or a ratio)
You use inverse sin (sometimes called arc sin) when you have the sides or the ratio and you are finding the angle!
So sine to find a side and inverse sin to find the angle.
sin(angle)=opphypsin−1(opphyp)=angle
sinh is a compicated thing that you probably wont use unless you study maths at a high level.
but if you are interested you can look here http://en.wikipedia.org/wiki/Hyperbolic_function