Let $a, b, c$ be the side lengths of an non-degenerate triangle with $a \le b \le c$. With $t (a, b, c)$ denote the minimum of the quotients $\frac{b}{a}$ and  $\frac{c}{b}$ . Find all values that $t (a, b, c)$ can take.

1. Let \( a, b, c \) be the side lengths of a non-degenerate triangle with \( a \le b \le c \). We need to find the possible values of \( t(a, b, c) \), which is defined as the minimum of the quotients \( \frac{b}{a} \) and \( \frac{c}{b} \).

2. Define \( x = \frac{b}{a} \) and \( y = \frac{c}{b} \). Since \( a \le b \le c \), it follows that \( x \ge 1 \) and \( y \ge 1 \). Therefore, \( t(a, b, c) = \min\{x, y\} \ge 1 \).

3. The side lengths can be expressed as \( b = ax \) and \( c = axy \). For the triangle to be non-degenerate, the triangle inequality must hold:
   \[
   a + b > c \implies a + ax > axy \implies 1 + x > xy \implies x(y - 1) < 1.
   \]

4. Consider the case when \( x = 1 \) or \( y = 1 \):
   - If \( x = 1 \), then \( b = a \) and \( c = ay \). The condition \( 1 + x > xy \) simplifies to \( 2 > y \), which is always true since \( y \ge 1 \). Thus, \( t(a, b, c) = 1 \).
   - If \( y = 1 \), then \( c = b \) and \( b = ax \). The condition \( 1 + x > xy \) simplifies to \( 1 + x > x \), which is always true. Thus, \( t(a, b, c) = 1 \).

5. For \( x > 1 \) and \( y > 1 \), we consider two cases:
   - **Case 1: \( x \le y \)**. Then \( t(a, b, c) = x \). The condition \( x(y - 1) < 1 \) implies:
     \[
     x(y - 1) < 1 \implies x(x - 1) \le x(y - 1) < 1 \implies x^2 - x - 1 < 0.
     \]
     Solving the quadratic inequality \( x^2 - x - 1 < 0 \) gives:
     \[
     x < \frac{1 + \sqrt{5}}{2}.
     \]
     Therefore, \( t(a, b, c) = x < \frac{1 + \sqrt{5}}{2} \).

   - **Case 2: \( x \ge y \)**. Then \( t(a, b, c) = y \). The condition \( x(y - 1) < 1 \) implies:
     \[
     x(y - 1) < 1 \implies y(y - 1) \le x(y - 1) < 1 \implies y^2 - y - 1 < 0.
     \]
     Solving the quadratic inequality \( y^2 - y - 1 < 0 \) gives:
     \[
     y < \frac{1 + \sqrt{5}}{2}.
     \]
     Therefore, \( t(a, b, c) = y < \frac{1 + \sqrt{5}}{2} \).

6. Combining the results from all cases, we have:
   \[
   1 \le t(a, b, c) < \frac{1 + \sqrt{5}}{2}.
   \]

7. For any \( k \in \left[1, \frac{1 + \sqrt{5}}{2}\right) \), we can construct a triangle with \( t(a, b, c) = k \) by setting \( \frac{b}{a} = \frac{c}{b} = k \).

Hence, the possible set of values for \( t(a, b, c) \) is the interval \( I = \left[1, \frac{1 + \sqrt{5}}{2}\right) \).

The final answer is \( \boxed{ \left[1, \frac{1 + \sqrt{5}}{2}\right) } \).