21Suppose the curve y f(x)crossing point (is located in the first quadrant,theintersection point between the normal line at any point P(x,y)and the Y-axis is Q.,andthe line segment PQ is bisected by the X-axis.(①)Find the equation of the curve y=f(x);()Given that the arc length of the curve y sinx at [0,is l,use l to representthe arc length s of the curve y f(x).