Hey

I am trying to calculate the streamline ofu=(ay, -ax, 0)

I know i need to solve this set of differential equations:

dx/ds = ay, dy/ds= -ax , dz/ds=0

I am supposed to get a solution of:

x = yo sin (as) + xo cos (as)

y = yo cos (as) - xo sin (as)

z = zo

where xo, yo, zo are the intial conditions.

I don't understand where the sin and cos have come from.

Thank you for any help