Substitution of symbols in equation after their values are being calculated

i have Fallowing Equation

syms yApprox(X1) a0 a1 a2 a3 a4 a5 a6
yApprox = a0 + a1*X1 + a2*X1^2 + a3*X1^3+ a4*X1^4 + a5*X1^5 + a6*X1^6; 

i have calculated values of a0 a1 a2 a3 a4 a5 a6, In order to express the equation in therms of these values Now i want to substitute them in equation how i can do that???

Answer 1

[Star Strider]

Try this —

syms yApprox(X1) a0 a1 a2 a3 a4 a5 a6
syms a2 a3 a4 a5 a6
EQ_01=a2 +9*a3 + 72*a4 + 540*a5 + 3888*a6 == -121/36000;
EQ_02=a3+ a2/12 +9*a4 +72*a5 +540*a6 == -1049/7776000;
EQ_03=a4 + (5*a2)/648 + (5*a3)/48 + (25*a5)/3 + (450*a6)/7 == -2987/419904000;
EQ_04 =a5 + (7*a2)/8640 + (7*a3)/600 + (7*a4)/60 + (63*a6)/8 == -19789/41990400000;
EQ_05 =a6 + a2/10800 + a3/720 + a4/70 + a5/8 == -24163/661348800000;
sol = solve([EQ_01, EQ_02, EQ_03, EQ_04, EQ_05],[a2,a3,a4,a5,a6])

sol = struct with fields:
    a2: -265660443171156185011/26563311466141754327040
    a3: 36806947866579283561/39844967199212631490560
    a4: 8376188234952364463/956279212781103155773440
    a5: -76519827268723512571/14344188191716547336601600
    a6: 21255507574645885373/143441881917165473366016000

a2 =  vpa(sol.a2)

a2 = 

a3 =  vpa(sol.a3)

a3 = 

0.00092375400091448985737373823903909

a4 =  vpa(sol.a4)

a4 = 

0.0000087591449474178977579770895298368

a5 =  vpa(sol.a5)

a5 = 

a6 =  vpa(sol.a6)

a6 = 

0.00000014818201832377291812525209972859

yApprox = a0 + a1*X1 + a2*X1^2 + a3*X1^3+ a4*X1^4 + a5*X1^5 + a6*X1^6; 

yApprox = subs(yApprox)

yApprox = 

yApprox = vpa(yApprox, 6)                                   % Easier To Read, Retains Full Precison

yApprox = 

Use the subs funciton to automatically (in this instance) substitute the appropriate variables.

.

[inzamam shoukat]

thanks alot it work

[Star Strider]

As always, my pleasure!