Question solve(eqn)

Hello, I'm wondering, how can we take the values of the different variables which where found by the function 'solve' and use them for another calculation ? I wrote this and i need the values of a0, a1, a2, a3, a4 and a5 for the calculation of f7.

syms a0 a1 a2 a3 a4 a5 
v = [0 2 4 6 8 10]
f = [0 2.9 14.8 39.6 74.3 119]
f1 = a0 + a1*v(1) +  a2*v(1)^2 + a3*v(1)^3 + a4*v(1)^4 + a5*v(1)^5 == 0
f2 = a0 + a1*v(2) +  a2*v(2)^2 + a3*v(2)^3 + a4*v(2)^4 + a5*v(2)^5 == 2.9
f3 = a0 + a1*v(3) +  a2*v(3)^2 + a3*v(3)^3 + a4*v(3)^4 + a5*v(3)^5 == 14.8
f4 = a0 + a1*v(4) +  a2*v(4)^2 + a3*v(4)^3 + a4*v(4)^4 + a5*v(4)^5 == 39.6
f5 = a0 + a1*v(5) +  a2*v(5)^2 + a3*v(5)^3 + a4*v(5)^4 + a5*v(5)^5 == 74.3
f6 = a0 + a1*v(6) +  a2*v(6)^2 + a3*v(6)^3 + a4*v(6)^4 + a5*v(6)^5 == 119
solve (f1, f2, f3, f4, f5, f6)
% Lorsque le projectile se déplace à la vitesse de 750 ft/sec, la force de
% ce même projectile est : 
v(7) = 750;
% Calcul de la force
f7 = a0 + a1*v(7) +  a2*v(7)^2 + a3*v(7)^3 + a4*v(7)^4 + a5*v(7)^5

Answer 1

[Torsten]

Replace

solve (f1, f2, f3, f4, f5, f6)

by

[a0,a1,a2,a3,a4,a5] = solve (f1, f2, f3, f4, f5, f6)

But note that extrapolating the function from the interval [0 10] for v to v = 750 is doubtful.

[Jothi]

Ok, thanks for the answer !

Answer 2

[Walter Roberson]

syms a0 a1 a2 a3 a4 a5 
v = [0 2 4 6 8 10]

v = 1×6

0 2 4 6 8 10

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f = [0 2.9 14.8 39.6 74.3 119]

f = 1×6

0 2.9000 14.8000 39.6000 74.3000 119.0000

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f1 = a0 + a1*v(1) +  a2*v(1)^2 + a3*v(1)^3 + a4*v(1)^4 + a5*v(1)^5 == f(1)

f1 = 

f2 = a0 + a1*v(2) +  a2*v(2)^2 + a3*v(2)^3 + a4*v(2)^4 + a5*v(2)^5 == f(2)

f2 = 

f3 = a0 + a1*v(3) +  a2*v(3)^2 + a3*v(3)^3 + a4*v(3)^4 + a5*v(3)^5 == f(3)

f3 = 

f4 = a0 + a1*v(4) +  a2*v(4)^2 + a3*v(4)^3 + a4*v(4)^4 + a5*v(4)^5 == f(4)

f4 = 

f5 = a0 + a1*v(5) +  a2*v(5)^2 + a3*v(5)^3 + a4*v(5)^4 + a5*v(5)^5 == f(5)

f5 = 

f6 = a0 + a1*v(6) +  a2*v(6)^2 + a3*v(6)^3 + a4*v(6)^4 + a5*v(6)^5 == f(6)

f6 = 

sol = solve([f1, f2, f3, f4, f5, f6])

sol = struct with fields:
    a0: 0
    a1: 137/80
    a2: -1147/960
    a3: 127/192
    a4: -269/3840
    a5: 1/384

% Lorsque le projectile se déplace à la vitesse de 750 ft/sec, la force de
% ce même projectile est : 
v(7) = 750;
% Calcul de la force
f7 = subs(a0 + a1*v(7) +  a2*v(7)^2 + a3*v(7)^3 + a4*v(7)^4 + a5*v(7)^5, sol)

f7 =