In this problem we know tht one side of the square is equal to 60, and we know that if an angle is part by the halve then the angle will be 45 degrees so we can draw an imaginari horizontal line to have a small triangle like this:
Now we can use the pythagorical theorem so where:

so:

Now we simplify ad solve for d so:
![\begin{gathered} 3600=(d^2)/(4)+(d^2)/(4) \\ 3600=(2d^2)/(4)=(d^2)/(2) \\ 3600\cdot2=d^2 \\ d=\sqrt[]{7200} \\ d=84.85 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/phufbcvi8hhr0vge3yu76cdt1m8f3vain6.png)