L=∫a,b(√(x`(t)^2+y`(t)^2)
x`=4cost^3=12sint^2*cost x`^2=144sint^4cost^2
y`=4sint^3=-12sint*cost^2 y`^2=144sint^2cost^4
√(x`(t)^2+y`(t)^2)=√(144sint^4cost^2+144sint^2cost^4)=12|sintcost|
l=∫0,pi/6(12|sintcost|dt|=∫0,pi/6(12sintcost)dt=6∫0,pi/6(sin2t)dt=6(-cos2t/2)|pi/6,0=
6(-cos(2*pi/6)/2-(-cos0)=6(1/2+1)=6*1,5=9