Find the length of the diagonal of the prism. 12, 3, 4

To find the length of the diagonal of a prism, we can use the Pythagorean theorem.

Let the sides of the base of the prism be a = 12 and b = 4, and the height of the prism be c = 3.
The diagonal of the base can be found using the Pythagorean theorem:

d1 = sqrt(a^2 + b^2)
= sqrt(12^2 + 4^2)
= sqrt(144 + 16)
= sqrt(160)
= 12.65

The diagonal of one of the rectangular faces of the prism is equal to this value, d1 = 12.65.

The diagonal of the prism can be found by using the Pythagorean theorem again, now considering the height of the prism.

d2 = sqrt(d1^2 + c^2)
= sqrt(12.65^2 + 3^2)
= sqrt(160.0225 + 9)
= sqrt(169.0225)
= 13

Therefore, the length of the diagonal of the prism is 13.