Use differentials to solve the problem:
The Louvre Pyramid is a tourist attraction in Europe. It is a square pyramid, with a height of $21 m$, and base of side length $35 m$. The four faces of this pyramid are covered in glass, of thickness $0.03 m$. Find the volume of glass used to construct the exterior of the Louvre.
I know that the volume of a square pyramid is: $V=\frac{a^2h}{3}$, where $a$ is its base length and $h$ is its height.
I then solved for $dV=\frac{a^2\ dh + 2ah\ da}{3}$, but I am stuck in this equation because there are many unknowns.
The next step I can think of is finding the volume, which can be in the form of: $V_{Glass}=V(Value+0.03)-V(Value)$, which can be evaluated like: $L(x)=f(x_0)+f'(x_0)(x-x_0)$, but I am not sure of the way of finding the $V(Value)$.
Why do you think you have many unknown in this formula ? $$dV=\frac{a^2\ dh + 2ah\ da}{3}$$
You have all the information that you need to find your dV.
The only apparently unknown is $d$ which could be found by $$dh=\frac {3}{\sin \alpha} $$ where $$\tan \alpha = \frac {a}{2h}$$