Step-by-step explanation:
the area of a triangle is always
baseline × height / 2
where baseline and height are perpendicular (with a 90° angle) to each other.
it does not matter, if the height is inside or outside of the triangle.
so, in our case the area is
4×5/2 = 2×5 = 10 units²
inverse means opposite,
inverse of addition is subtraction
This is an altitude. Shown by the right angle on the side opposite the point.