Area of a right triangle is product of the 2 legs divided by 2. That's it.
The area of any right angled triangle is or half base times height. For a right angled triangle the base and the height are the two smaller sides (ab in my example). The perimeter of a right angled triangle is the sum of it's three sides: but from Pythagoras we know that it's also equal to .
Perimeter and area for right angled triangles are often easy enough to calculate without having to use such tricky formulae.
Edit: Could you speak in full English please? "u" and "ur" are frowned upon and makes the text harder to parse.