Trouble solving equation fsolve

Hi everybody,

I got some trouble solving this equation.The solution of the following equation is correct but i would like to solve the equation semplifying it, i.e. replacing my coefficients with letters. Othervise replacing my coefficients with vectors.

Ex. a=1.66 b=0.000127 c=2.5 d=0.000423

syms x

solve ('1.66/((9.81*x*0.000127)^(0.5))=6+2.5*log(x/(2.5*0.000423))',x)

ans =

3.2523216595041554101826783891542

Can anybody hel me?

I'm a beginner.

Answer 1

[John D'Errico]

Not sure what the problem is. And why are you asking about fsolve?

a = 1.66;
b = 0.000127;
c = 2.5;
d = 0.000423;
g = 9.81;
syms x
solve (a/sqrt(g*x*b) == 6 + c*log(x/(c*d)),x)

Warning: Unable to solve symbolically. Returning a numeric solution using vpasolve. 
> In solve (line 304) 
ans =
3.2523216595041553985081838768663

No symbolic solution was found, so it used vpasolve to find a numerical solution. wtp?

If you wanted a fully general analytical solution, tough luck. It is terribly easy to write an equation that has no analytcal solution. In fact, it seems you just did it.

Note my use of sqrt, insead of raising to a fractional power. Far easier to read.