@Preben Alsholm Thank you for your help. Now everything is clear for me.

@Preben Alsholm Thank you for your help. Now everything is clear for me.

Thank you for your answer but i have some questions regarding your solution.

I don't know where numerator and -2 in denumerator come from. I thought that if function is given in parametric form its derivate should be dy/dt/dx/dt.

Could you explain it to me?

Thank you for your answer but i have some questions regarding your solution.

I don't know where numerator and -2 in denumerator come from. I thought that if function is given in parametric form its derivate should be dy/dt/dx/dt.

Could you explain it to me?