Find the exact area (in square units) of triangle AOB with vertices A(0, 8), O(0, 0), and B(5, 0).

Introduction / Context:
With right-angled triangles aligned to the axes, area is quickly found by half the product of legs. Here AO is vertical and OB is horizontal, making a right angle at O.

Given Data / Assumptions:

• AO length = 8 units (along y-axis).
• OB length = 5 units (along x-axis).

Concept / Approach:
Area formula: A = (1/2) * base * height for right triangles.

Step-by-Step Solution:

Verification / Alternative check:
Shoelace formula with points (0,0), (5,0), (0,8) also gives 20.

Why Other Options Are Wrong:
They are arithmetic distractors unrelated to (1/2)*5*8.

Final Answer:
20 sq. units