Question

a diagonal of a rectangle is 15 cm if the length of the rectangle is 12 cm what will be the perimeter of this triangle

Answer 1

given, 
length of diagonal=15 cm
length= 12 cm
now,
Breadth² = diagonal² -  length²
 Breadth²  = 15² - 12²
  Breadth²  = 225 - 144
   Breadth²   =  81

therefore,
breadth = √81
              = 9 cm

now for the perimeter of the triangle= (15+ 12 +9 ) cm 
                                                     =36 cm

Answer 2

given, 
length of diagonal=15 cm
length= 12 cm
now,
B² = diagonal² -  length²
B²  = 15² - 12²
B  = 225 - 144
B²   =  81

So,
B = √81
              = 9 cm

now for the perimeter of the triangle= (15+ 12 +9 ) cm 
                                                     =36 cm