Question

Un romb cu perimetrul egal cu 20 de cm si o diagonala cu lungimea egala cu 6 cm are aria egala cu??

Answer 1

P=4l
P=20

4l=20  =>l=5

ΔABD
[AB]=[AD]=5
[BD]=6

A ΔABD =√p(p-a)(p-b)(p-c)

p=(5+5+6)/2=  16/2=8

A ΔABD=√8(8-5)(8-5)(8-6)=

=√2³ * 3 *3 *2=

=2² *3= 4*3=12

A ABCD=2*A ΔABD=  2*12=24cm²

Answer 2

P = 20 cm 
P = 4L 
L = 20 : 4 
L = 5 cm . 

Arie romb = d₁*d₂:2 .

d²/2 = 5² - 3²
d²/2 = 25-9
d²/2 = 16
d² = 8 cm . 
Arie romb =  d₁*d₂ /2 
Arie romb = 6*8/2 = 48/2 = 24 cm²