Split the triangle in half.
8.6cm is the hypotenuse and 8.6/2 is the length of base.
The Pythagorean theorem: a^2+b^2=c^2
So that means 8.6^2-4.3^2=height
= 73.96 - 18.49 = 55.47
So the square root of 55.47 is the height of the triangle.
The area of a triangle is h * b/2
So the base is 8.6 and the height is the square root of 55.47. 8.6/2=4.3
So 4.3 times the square root of 55.47 is the area.