



 
Hi Steve, I drew a diagram of what I think you are describing. Since the angle $ABC$ measures $45^o$ triangle $ABC$ is an isosceles triangle and the lengths $BC$ and $CA$ are equal. Hence the length $L$ is $84 + 2 \times BC \mbox{ inches }$ that is 84 inches plus twice the width of the board. Harley  


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences. 