为什么SymPy忽略了我的初始条件？

Question

import sympy as sp

t = sp.Symbol("t")
y = sp.Function("y")
v = sp.Function("v")

sol = sp.dsolve([
        y(t).diff(t) - v(t),
        v(t).diff(t) + 2*y(t)
    ],
    ics={y(0):2, v(0):0.45})
sol

给出：

[y(t) == C1*sin(sqrt(2)*t) + C2*cos(sqrt(2)*t),
 v(t) == sqrt(2)*C1*cos(sqrt(2)*t) - sqrt(2)*C2*sin(sqrt(2)*t)]

为什么不计算C1和C2？