答:
>>f='(-1)*exp(-(abs(x)))*abs(sin(cos(abs(x))))';
>>x=fminsearch(f,0),ymax=exp(-(abs(x)))*abs(sin(cos(abs(x))))
x =
0
ymax =
0.8415
1-6 设 D2y-3Dy+2y=x,y(0)=1,Dy(0)=0,求 y(0.5)旳值。
答:
>> f='D2y-3*Dy+2*y=x';g=dsolve(f,'y(0)=1,Dy(0)=0','x');x=0.5;y=eval(g)
y =
0.6100
1-7 求方程 cos(t)^2*exp(-0.1t)=0.5t 旳解。
答:
>>t1=solve('cos(t)^2*exp(-0.1*t)=0.5*t','t');t=eval(t1)
t =
0.8329
1-8 求方程组:x^2+y^2=1,xy=2 旳解。
答:
>>[x,y]=solve('x^2+y^2=1','x*y=2','x','y')
x =
-1/2*(1/2*5^(1/2)+1/2*i*3^(1/2))^3+1/4*5^(1/2)+1/4*i*3^(1/2)
-1/2*(1/2*5^(1/2)-1/2*i*3^(1/2))^3+1/4*5^(1/2)-1/4*i*3^(1/2)