dA(R-11 R s. T TCOS dr\R+12)(1+R) "(S,z)=()cos( d P =2Q(1+R)A-Q+ dt R-11 P 2OR stability 0+ R+12人c2)1+R inhomogeneous P(R-1 solution Q R+1 Q、R-1 P R+lI P Q R A Q ddI I R R A R R d dA ˆ ˆ 2 (1 ) ˆ ˆ (1 ) ˆ 1 1 1 ˆ 2 2 2 ⎟⎠⎞ ⎜⎝⎛ = + − + + ⎟ − ⎠⎞ ⎜⎝⎛ − +− = l l τ τ ( ) cos( ) ˆ '( , ) ( ) cos( ) ˆ '( , ) l l s I s I s A s A τ τ τ τ = = 0 1 1 1 0 1 1 2 1 1 2 2 2 2 ⎟ <⎠⎞ ⎜⎝⎛ − +− + − > + ⎟ +⎠⎞ ⎜⎝⎛⎟ + ⎠⎞ ⎜⎝⎛ − +− − l l l l R P R Q R P QR Q RR stability inhomogeneous solution 1 1 + − > R R P Q 8