We can calculate the sides of the square hole in the desk by using the sine law, which is the sine of an angle = the length of the opposite side divided by the length of the hypotenuse.
in algebraic terms, sine ∠A = opposite/hypotenuse
so, sine ∠A x hypotenuse = opposite
the sine of 45o is 0.7071, and the length of the hypotenuse is 24 inches
so, 0.7071 x 24 inches = the length of the opposite side = 17 inches
so, it appears that the monitor will not fit.