a square is made up of 2 congruent right triangles with the same leg length. we use the Pythagorean theorem to find the length of one of these legs. a^2+b^2=c^2, but we know that the legs are equal in length, so we have 2a^2=(3rad2)^2
2a^2=9*2
a^2=9
a=3
square is made up of 4 of these, so 4*3=12
the perimeter is 12
