Find the value of c.

The Pythagorean theorem states that in a right triangle, the square of the length of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the other two sides.

Applying this theorem to the given triangle, we have:

c^2 + 11^2 = 12^2

c^2 + 121 = 144

c^2 = 144 - 121

c^2 = 23

Taking the square root of both sides gives:

c = √23

Therefore, the value of c is the square root of 23.