Step 1: Using the area formula for a triangle:
\[
\text{Area} = \frac{1}{2} \times \text{Base} \times \text{Height}.
\]
Step 2: Identifying base and height:
\[
\text{Base} = a, \quad \text{Height} = b.
\]
Step 3: Computing area:
\[
\text{Area} = \frac{1}{2} \times a \times b = \frac{1}{2} ab.
\]