First, find the length of the ladder, which is the hypotenuse in this scenario.
[tex]a^2 + b^2 = c^2\\5^2 + 12^2 = c^2\\c = 13[/tex]
Then, find the new height once the ladder has slid:
[tex]a^2 + b^2 = c^2\\6^2 + b^2 = 13^2\\b = 11.53[/tex]
The ladder reaches about 11.53 feet up the pole.