Question

What is a formula that can be used to find the area of one triangular section of the door? How do you know the formula will work?

Answer 1

Answer:

$\frac{1}{2} * length * breadth$

Explanation:

We know that the area of a complete rectangle is length * breadth.

The door is a rectangle. If we divide it into two triangles (there's only one way we can do that: using the diagonal), we'll get two IDENTICAL triangles. Each of the two triangles will be exactly the same as the other, so naturally we can say that their areas must also be equal.

Now let the area of one triangle be x.

Then total area = x + x = 2x.

Now, 2x must be equal to the total area of the door, which we know to be length * breadth.

So x is half of length * breadth.