1. A dolphin is swimming such that it is diving in and out of the sea at a constant speed.

The height, $h$ cm, of the dolphin, relative to sea level $(h=0)$, at time $t$ sconds, is to be modelled using the formula  $h=Asin(Bt)$  where $A$ are $B$ constants.

On each jump and dive the dolphin reaches a height of 70 cm above sea level and a depth of 70 cm below sea level. Write down the value of $a$.