Answer:
13 square units
Step-by-step explanation:
You <em>could</em> calculate the length of each side using Pythagorean theorem, then use Heron's formula to find the area. But there's an easier way: find the area of the rectangle that contains the triangle, and subtract the areas of the smaller triangles in the corners.
The area of the rectangle is 4 × 7 = 28.
The area of the upper left triangle is ½(2)(4) = 4.
The area of the upper right triangle is ½(3)(5) = 7.5.
The area of the lower right triangle is ½(1)(7) = 3.5.
So the area of the triangle is:
28 − 4 − 7.5 − 3.5 = 13
