In a right-angled isosceles triangle, two sides are equal in length and meet at a 90° angle.
Let the two equal sides each have length a cm.
The hypotenuse is given as A cm.
By the Pythagorean theorem:
a2+a2=A2
2a2=A2
a2=2A2
The two equal sides are perpendicular to each other, so they serve as the base and height of the triangle.
Area =21×base×height
Area =21×a×a
Area =21×a2
Substituting a2=2A2:
Area =21×2A2
Area =4A2
Therefore, the area of the triangle is 4A2 square cm.