Answer:
A.

Explanation:
From Geometry, we know that the area of the triangle (
) is equal to:
(1)
Where:
- Base.
- Height.
By Pythagorean Theorem, we derive expressions for the base and the height of triangle. That is:

(2)

(3)
By (2) and (3), we expand (1):

Hence, correct answer is A.