求解代码。实在写不出来

两道题的代码

同学你好，这个都是一个意思：
3（1）

function s =  fun1(n)
k = 1:n;
s = sum(1./(k.*(k+1)));
end

3（2）

function s =  fun2(n)
k = 1:n;
s = sum((2+(-1).^(k))./2.^k;
end

3（3）

function s =  fun3(n)
k = 1:n;
s = sum(1./factorial(k-1));
end

3（3）

function s =  fun4(n)
k = 1:n;
s = sum(sqrt(k+1).*(1-cos(pi./k)));
end

4
(1)

x=linspace(0,2*pi,100);
figure(1)
subplot(2,2,1)
plot(x,sin(5*x));
subplot(2,2,2)
plot(x,cos(3*x));
subplot(2,2,3)
plot(x,sin(5*x).*cos(3*x));
subplot(2,2,4)
plot(x,sin(5*x)+cos(3*x));

(2)

x=linspace(0,2*pi,100);
plot(x,sin(x),'r-')
hold on
plot(x,sin(5*x))
plot(x,sin(x)+sin(5*x))
legend('sinx','sin5x','sin(x)+sin(5x)')