Question

Diketahui keliling belah ketupat 40 cm.jika panjang salah satu diagonalnya 12 cm maka luas belah ketupat tersebut adalah...cm²

Answer 1

D = 1/2 x 12 = 6 cm
s = 40 : 4 = 10 cm
diagonal lainnya
d = 2 x √ 10² - 6²
   = 2 x √100 - 36
   = 2 x √64
   = 2 x 8
   = 16 cm
luas = 16 x 12 /2
       = 16 x 6
       = 96 cm²

Answer 2

K belah ketupat = 4 x sisi miring
40 = 4.s
40/4 = s
s = 10

s² = (1/2 d₁)² + (1/2 d₂)²
10² = 6² + (1/2 d₂)²
100 = 36 + (1/2 d₂)²
100 - 36 = (1/2 d₂)²
64 = (1/2 d₂)²
1/2 d₂ = √64
1/2 d₂ = 8 cm
d₂ = 8.2
d₂ = 16 cm

L = 1/2 x d₁ x d₂
L = 1/2 x 12 x 16
L = 6 x 16
L = 96 cm²