Hi all,

it is just a curious question. I am calculating `k`

from this

\int_{0}^{180} kx^{2} (180 - x) dx = 1

solving for k I should obtain \frac{1}{87,480,000} but why the answer contains 1-element Vector? instead of just the number?

```
using SymPy
@syms x, k
a,b = 0, 180
k1 = solve(integrate(k*(x^2)*(180-x),(x,a,b)) ~ 1, k)
```

```
1-element Vector{Sym}:
1/87480000
```

jling
February 21, 2023, 5:57am
2
that’s just how the interface works. My guess is to make type stable – i.e. you don’t get `Sym`

vs. `Vector{Sym}`

depending on how many variables you have, which is a runtime property

4 Likes

There is this problem I try:

```
k1::Vector
```

1-element Vector{Sym}:
95802719.0924019

```
k1::Int64
```

TypeError: in typeassert, expected Int64, got a value of type Vector{Sym}
Stacktrace:

I want to turn `k1`

into integer or float… how?

I’m a big fan of `only(k1)`

in this situation. It’s the same thing as `k1[1]`

except it will throw an error if `length(k1) != 1`

.

3 Likes