% 练习1
x=linspace(-pi,pi,21)
y=sin(x)
% 练习2
clear
k=1:1000;
kk=1./k;
kkk=kk./k;
res=sum(kkk)-(pi^2)/6
% 练习3
sum(kk-log(1000))
% 练习4
clear
a=rand(2,3)
x=a(1,:)
y=a(2,:)
norm(x)
norm(y)
acos(dot(x,y)/norm(x)/norm(y))
% 练习5
clear
rand(3)
det(ans)  % 线性无关
% 练习6
clear
a=rand(3,2)
x=a(1,:)
y=a(2,:)
z=a(3,:)
alpha=x-z
beta=y-z
alpha=[alpha 0]
beta=[beta 0]
cross(alpha,beta)
% 练习7
clear
a=11:19
b=a
for k=1:8
    b=[b;a+10*k];
end
rank(b)
% 练习8
y=[]
for x=-6:0.05:6
    y=[y difun(x)];
end
plot(x,y)
plot([-6:0.05:6],y)
% 练习9
A=[6,2,1,-1;2,4,1,0;1,1,4,-1;-1,0,-1,3];
b=[6;1;5;-5]
x=A\b
% 练习10
[diag(1:4) eye(4)]
% 练习11
num2p(123453656345)
% 练习12
ttry(100)