Answer:

Step-by-step explanation:
Given:
The above triangle
Required
Solve for AB in terms of a, b and angle C
Considering right angled triangle BOC where O is the point between b-x and x
From BOC, we have that:

Make h the subject:

Also, in BOC (Using Pythagoras)

Make
the subject

Substitute
for h
becomes


Factorize

In trigonometry:

So, we have that:

Take square roots of both sides

In triangle BOA, applying Pythagoras theorem, we have that:

Open bracket

Substitute
and
in 


Open Bracket

Reorder

Factorize:

In trigonometry:

So, we have that:


Take square roots of both sides

Well, notice the composite is really just 4 triangles atop sitting on top of 4 rectangles, and all of them area stacked up at the edges.
so, for the rectangle's sides,
front and back are two 6x3 rectangles
left and right are two 6x3 rectangles
the bottom part is a 6x6 rectangle
now, we don't include the 6x6 rectangle that's touching the triangles, because that's inside area, and is not SURFACE area, so we nevermind that one.
now, the triangles are just four triangles with a base of 6, and a height of 4, in red noted there.
so, just get the area of all those rectangles and the triangles, sum them up and that's the
surface area of the composite,
The percent discount was,
55.5556. It could be changed to 56%, but as a whole it would more than likely be 55%.
-Mabel <3