Use vpasolve (or other function) to solve a system nonlinear equation with known variables in a specified range

Hello everyone,

Can you help me solve my problem?

My problem is : Use vpasolve

(or other function in matlab) to solve a system nonlinear equation with known variables in a specified range!

t1= 10;
20<t2<21;
30<t3<31;
40<t4<41;
t5=50;
eq1=atan(f1)-atan(f2)-(t1/2+t2/2);
eq2=(atan(-f1)^-1)-(atan(-f2)^-1)-(deg2rad(180)-t1/2-t2/2);
eq3=atan(f2)-atan(f3)-(t2/2+t3/2);
eq4=atan(f3)-atan(f4)-(t3/2+t4/2);
eq5=atan(f4)-atan(f5)-(t4/2+t5/2);
eqs = [eq1, eq2, eq3, eq4, eq5];
F = [f1, f2, f3, f4, f5];
a = deg2rad(360);
for n=1:10
    [F1,F2,F3,F4,F5] = vpasolve(eqs,F,[0 a;0 a;0 a;0 a;0 a],'Random',true);
end

because t2,t3,t3 and t4 are not fix (so are variable in a range) matlab can not solve!

how can solve this?

thank you.