Bandpass Dilemma!

Sup all! I need someone who knows how to do trigenomotry. I have decided to build a bandpass sub box for my subs. Mainly due to my existing box's cosmetic design and the specifications do not meet the subs parameters.

I have put alot of thought in this. And have concluded this box will be the best for my interest relating to my vehicle. I should inform you all on the dimensions and specifics of the design. (So you know what the variables are)

Specifically and strictly designed around the subs specs., the box contains the manufacturers recommended port size and volume.

Subwofoer Box Dimensions:

#7 is the two pieces of wood that the sub mounts onto. If I remember correctly, a tablesaw can only cut to a maximum of 45 degree angles. Therefore, the sub inside the box is angled at a 45 degree angle. Although, the problem herein lies. In order to find out what #7's length are, I must first apply trigenomotry to the problem.

But I cannot! It has been a minute since I have worked with triangles. So, that is why I ask for someones help! Please, someone help me out!

Or maybe yet, you could give me the formula to figure out the sides using the 45,45,90 degree triangle.

I only have one measurement. That is the distance from the front of the sub box to the rear. 14 and 1/4 inch. I remember in my math class that we could use an angle measure and the side length to figure out one other of the sides lengths. Then just put those two together to find the last length.

Eh, I dunno though. I really need to refresh my mind... I'm stumped, haha. Sorry man.