To find the distance between two points \( A(1, 5) \) and \( B(5, 2) \) on a coordinate plane, we can use the distance formula:
\[ d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \]
Here, \( A(1, 5) \) gives us \( (x_1, y_1) = (1, 5) \) and \( B(5, 2) \) gives us \( (x_2, y_2) = (5, 2) \).
Now, substituting the coordinates:
\[ d = \sqrt{(5 - 1)^2 + (2 - 5)^2} \]
Calculating the differences:
\[ d = \sqrt{(4)^2 + (-3)^2} \]
Calculating the squares:
\[ d = \sqrt{16 + 9} \]
Adding the values:
\[ d = \sqrt{25} \]
Taking the square root:
\[ d = 5 \]
Thus, the distance between points \( A \) and \( B \) is \( 5 \) units.