Question

explain in short method​

Answer 1

Answer:

perimeter of triangle DEF is 12cm

Step-by-step explanation:

in short you know D is midpoint i.e AD = BD =8 cm therefore DE = 4 cm ( equilateral triangle)

we know perimeter of equilateral triangle= 3 a

3 × 4= 12cm

Answer 2

Step-by-step explanation:

In ∆ABC,

AB= BC=CA ... ( sides of an equilateral ∆)

AB= 8cm

therefore,

DE= 1/2 AB .... (1)( Midpoint theorem)

EF=1/2BC .... (2)

DF= 1/2CA ... (3)

therefore,

DE=EF=DF .... (4) ( from(1),(2)&(3))

DE= 1/2×8 .... (5) ( from(1))

= 4 cm

In∆DEF,

Perimeter = DE + EF+DF

= 4+4+4 ..... (from(4)&(5))

=12 cm