Answer: hello your question is vague hence i will provide a more general answer
Area of a right angled triangle = 1/2 * b * h
Explanation:
For a right- angled triangle; the sum of squares of the opposite and adjacent sides = square of the longest side ( i.e. hypothenuse )
hence the Area of a right angled triangle = 1/2 * b * h
where : b = adjacent , h = opposite side