In this week, I figured out an important question:

Now we know that in this cuboid, Height equals c, Width equals b, and Length equals a. We should give a equation to express d.

How to figure out the equation?

First, add a new line. We named it “e”

Second, use the Pythagorean theorem.so

Because a^2 + b^2= c^2

So e^2=a^2+b^2, and d^2=c^2+e^2

So d^2=a^2 + b^2 + c^2

at last, use radical sing to calculate a precise number of d.