U(r) =
1
2
kr
2
(4.1)
xy
M
¨x = −ω
2
x , ¨y = −ω
2
y , ω =
r
k
m
, (4.2)
x(t) = A cos (ωt + α) , y(t) = B cos (ωt + β) , (4.3)
A, B, α β
cos(ωt + β) = cos δ cos(ωt + α) −sin δ si n(ωt + α) , δ = β −α ,
y = x
B
A
cos δ − B sin δ sin(ωt + α)
cos
2
(ωt + α) + sin
2
(ωt + α) =
=
x
2
A
2
+
1
B
2
sin
2
δ
y −
B
A
x cos δ
2
= 1 . (4.4)