let   = @

 

y = a(1-cos@ )

 

dy/d@ = a ( sin@) ......................(1)

 

x = a ( @ - sin@ )

 

dx/d@ = a (1 - cos @) ..................(2)

 

eqn. (1) /(2)

 

dy/dx= (sin@) / (1 - cos@) = [1+ cos@ ] / sin@ .............(ans)