3.验证下列各函数是相应微分方程的解:-|||-(1) =dfrac (sin x)(x) ,'+y=cos x ;-|||-(2) =2+csqrt (1-{x)^2} ,(1-(x)^2)y'+xy=2x (c是任意常数);-|||-(3) =c(e)^x ,y''-2y'+y=0 (c是任意常数);-|||-(4) =(e)^x ,'(e)^-x+(y)^2-2y(e)^x=1-(e)^2x ;-|||-(5) =sin x ,'+(y)^2-2ysin x+(sin )^2x-cos x=0 ;-|||-(6) =-dfrac (1)(x) ,^2y'=(x)^2(y)^2+xy+1 :-|||-(7) =(x)^2+1 ,'=(y)^2-((x)^2+1)y+2x ;-|||-(8) =-dfrac (g(x))(f(x)) ,'=dfrac (f'(x))(g(x))(y)^2-dfrac (g'(x))(f(x)) .